Switch CARBON_CHECK to a format string API (#4285)

This switches `DCHECK` and `FATAL` as well.

The goal is to reduce the code size impact of these assertions so that
we can keep more of them enabled. Currently, the largest cost I see from
`CHECK` is not the actual check or the cold code itself, but actually
the failure to inline trivial functions due to the presence of the cold
code. This means that our goal isn't to reduce apparent code size in the
final binary but the LLVM IR cost assessed for these routines in the
inliner, which closely correlates with code size but is a bit different.

As discussed in #4283, experimentation shows that a single function call
with a minimal number of arguments is the lowest cost model for these.
This is easily achieved with a format-string API that internally uses
`llvm::formatv`. This PR is essentially the `CHECK` version of #4283.

However, the check macros are substantially harder to make work with
both format strings and streaming because they also take a condition.
Also, unexpectedly, I was very successful at devising a regular
expression based automated rewrite from the streaming to the format
string form with only low 10s of manual fixes. This includes compacting
strings broken up across lines, etc. Given how well that went, I've
prepared this PR which just directly switches to the format string API
and migrate everything to use it.

One nice side-effect is that the format string approach ends up greatly
simplifying the implementation here as well.

This is ... *shockingly* effective. Parsing speeds up by more than 3%
with just this change. And checking speeds up by **8%** with this change
alone:
```
BM_CompileAPIFileDenseDecls<Phase::Parse>/256      86.3µs ± 1%  82.9µs ± 1%  -3.94%  (p=0.000 n=17+19)
BM_CompileAPIFileDenseDecls<Phase::Parse>/1024      431µs ± 1%   415µs ± 1%  -3.76%  (p=0.000 n=18+19)
BM_CompileAPIFileDenseDecls<Phase::Parse>/4096     1.77ms ± 1%  1.71ms ± 1%  -3.18%  (p=0.000 n=18+19)
BM_CompileAPIFileDenseDecls<Phase::Parse>/16384    7.44ms ± 1%  7.17ms ± 2%  -3.56%  (p=0.000 n=18+20)
BM_CompileAPIFileDenseDecls<Phase::Parse>/65536    30.7ms ± 1%  29.7ms ± 1%  -3.15%  (p=0.000 n=18+20)
BM_CompileAPIFileDenseDecls<Phase::Parse>/262144    131ms ± 1%   127ms ± 1%  -2.81%  (p=0.000 n=18+18)
BM_CompileAPIFileDenseDecls<Phase::Check>/256       878µs ± 2%   800µs ± 1%  -8.91%  (p=0.000 n=19+20)
BM_CompileAPIFileDenseDecls<Phase::Check>/1024     1.88ms ± 2%  1.72ms ± 1%  -8.56%  (p=0.000 n=19+20)
BM_CompileAPIFileDenseDecls<Phase::Check>/4096     5.78ms ± 2%  5.28ms ± 1%  -8.70%  (p=0.000 n=20+18)
BM_CompileAPIFileDenseDecls<Phase::Check>/16384    21.9ms ± 1%  20.1ms ± 1%  -8.02%  (p=0.000 n=18+20)
BM_CompileAPIFileDenseDecls<Phase::Check>/65536    90.4ms ± 2%  83.1ms ± 1%  -8.04%  (p=0.000 n=19+20)
BM_CompileAPIFileDenseDecls<Phase::Check>/262144    381ms ± 2%   352ms ± 1%  -7.79%  (p=0.000 n=19+19)
```

---------

Co-authored-by: Richard Smith <richard@metafoo.co.uk>
Co-authored-by: josh11b <15258583+josh11b@users.noreply.github.com>

toolchain/check/generic.cpp

@@ -73,9 +73,10 @@ class RebuildGenericConstantInEvalBlockCallbacks final
     if (!const_id.is_valid()) {
       // An unloaded import ref should never contain anything we need to
       // substitute into. Don't trigger loading it here.
-      CARBON_CHECK(context_.insts().Is<SemIR::ImportRefUnloaded>(inst_id))
-          << "Substituting into instruction with invalid constant ID: "
-          << context_.insts().Get(inst_id);
+      CARBON_CHECK(
+          context_.insts().Is<SemIR::ImportRefUnloaded>(inst_id),
+          "Substituting into instruction with invalid constant ID: {0}",
+          context_.insts().Get(inst_id));
       return true;
     }
     if (!const_id.is_symbolic()) {
@@ -174,9 +175,9 @@ static auto AddGenericConstantToEvalBlock(
       SubstInst(context, const_inst_id,
                 RebuildGenericConstantInEvalBlockCallbacks(
                     context, generic_id, region, constants_in_generic));
-  CARBON_CHECK(new_inst_id != const_inst_id)
-      << "Did not apply any substitutions to symbolic constant "
-      << context.insts().Get(const_inst_id);
+  CARBON_CHECK(new_inst_id != const_inst_id,
+               "Did not apply any substitutions to symbolic constant {0}",
+               context.insts().Get(const_inst_id));
   return context.constant_values().Get(new_inst_id);
 }
 
@@ -192,9 +193,9 @@ static auto PopulateConstantsFromDeclaration(
   for (auto inst_id : decl_eval_block) {
     auto const_inst_id = context.constant_values().GetConstantInstId(inst_id);
     auto result = constants_in_generic.Insert(const_inst_id, inst_id);
-    CARBON_CHECK(result.is_inserted())
-        << "Duplicate constant in generic decl eval block: "
-        << context.insts().Get(const_inst_id);
+    CARBON_CHECK(result.is_inserted(),
+                 "Duplicate constant in generic decl eval block: {0}",
+                 context.insts().Get(const_inst_id));
   }
 }
 
@@ -252,12 +253,13 @@ static auto MakeGenericEvalBlock(Context& context, SemIR::GenericId generic_id,
     }
   }
 
-  CARBON_CHECK(num_dependent_insts ==
-               context.generic_region_stack().PeekDependentInsts().size())
-      << "Building eval block added new dependent insts, for example "
-      << context.insts().Get(context.generic_region_stack()
-                                 .PeekDependentInsts()[num_dependent_insts]
-                                 .inst_id);
+  CARBON_CHECK(
+      num_dependent_insts ==
+          context.generic_region_stack().PeekDependentInsts().size(),
+      "Building eval block added new dependent insts, for example {0}",
+      context.insts().Get(context.generic_region_stack()
+                              .PeekDependentInsts()[num_dependent_insts]
+                              .inst_id));
 
   return context.inst_block_stack().Pop();
 }
@@ -283,11 +285,11 @@ auto RebuildGenericEvalBlock(Context& context, SemIR::GenericId generic_id,
     // Build a constant in the inst block.
     AddGenericConstantToEvalBlock(context, generic_id, region,
                                   constants_in_generic, inst_id);
-    CARBON_CHECK(context.inst_block_stack().PeekCurrentBlockContents().size() ==
-                 i + 1)
-        << "Produced "
-        << (context.inst_block_stack().PeekCurrentBlockContents().size() - i)
-        << " instructions when importing " << context.insts().Get(inst_id);
+    CARBON_CHECK(
+        context.inst_block_stack().PeekCurrentBlockContents().size() == i + 1,
+        "Produced {0} instructions when importing {1}",
+        (context.inst_block_stack().PeekCurrentBlockContents().size() - i),
+        context.insts().Get(inst_id));
   }
 
   return context.inst_block_stack().Pop();
@@ -299,9 +301,9 @@ auto FinishGenericDecl(Context& context, SemIR::InstId decl_id)
       context.scope_stack().compile_time_bindings_stack().PeekAllValues();
 
   if (all_bindings.empty()) {
-    CARBON_CHECK(context.generic_region_stack().PeekDependentInsts().empty())
-        << "Have dependent instructions but no compile time bindings are in "
-           "scope.";
+    CARBON_CHECK(context.generic_region_stack().PeekDependentInsts().empty(),
+                 "Have dependent instructions but no compile time bindings are "
+                 "in scope.");
     context.generic_region_stack().Pop();
     return SemIR::GenericId::Invalid;
   }
@@ -396,7 +398,7 @@ auto ResolveSpecificDefinition(Context& context, SemIR::SpecificId specific_id)
     -> bool {
   auto& specific = context.specifics().Get(specific_id);
   auto generic_id = specific.generic_id;
-  CARBON_CHECK(generic_id.is_valid()) << "Specific with no generic ID";
+  CARBON_CHECK(generic_id.is_valid(), "Specific with no generic ID");
 
   if (!specific.definition_block_id.is_valid()) {
     // Evaluate the eval block for the definition of the generic.