Add MakeVerifiedLocIdAndInst for runtime validation (#6942)

This follows up on a discussion about wanting to use `Any*` inst
clusters to handle boilerplate construction, with the issue that
`UncheckedLoc` use removes validation. Some context is at
https://github.com/carbon-language/carbon-lang/pull/6930#discussion_r2963157428.

This folds in `MakeImportedLocIdAndInst` because the logic is related,
particularly for `LocId` values which are `ImportIRInstId`, and it
eliminates questions of what the right function is to use.

This uncovers an error in the `NodeKind` associated with
`FormBindingPattern`. For now I'm just adding a TODO regarding that.

Assisted-by: Google Antigravity with Gemini

toolchain/check/cpp/operators.cpp

@@ -247,11 +247,12 @@ static auto MakeCppStdInitializerListMake(Context& context, SemIR::LocId loc_id,
                                    context, SemIR::IntLiteralType::TypeInstId),
                                .int_id = context.ints().Add(size)}));
   auto array_type_inst_id = AddTypeInst(
-      context, SemIR::LocIdAndInst::UncheckedLoc(
-                   loc_id, SemIR::ArrayType{
-                               .type_id = SemIR::TypeType::TypeId,
-                               .bound_id = bound_id,
-                               .element_type_inst_id = element_type_inst_id}));
+      context,
+      SemIR::LocIdAndInst::RuntimeVerified(
+          context.sem_ir(), loc_id,
+          SemIR::ArrayType{.type_id = SemIR::TypeType::TypeId,
+                           .bound_id = bound_id,
+                           .element_type_inst_id = element_type_inst_id}));
   auto array_type_id =
       context.types().GetTypeIdForTypeInstId(array_type_inst_id);