Prefix most macro names with CARBON_ (#1232)

I'm doing this to avoid macro name conflicts, following https://google.github.io/styleguide/cppguide.html#Preprocessor_Macros: "If you do export a macro from a header, it must have a globally unique name. To achieve this, it must be named with a prefix consisting of your project's namespace name (but upper case)."

Commands run:

```
sed -i 's/\(DCHECK\|CHECK\|FATAL\|MAKE_UNIQUE_NAME\|MAKE_UNIQUE_NAME_IMPL\|RAW_EXITING_STREAM\|RETURN_IF_ERROR\|RETURN_IF_ERROR_IMPL\|ASSIGN_OR_RETURN\|ASSIGN_OR_RETURN_IMPL\|DIAGNOSTIC_KIND\|RETURN_IF_STACK_LIMITED\)(/CARBON_\1(/g' $(git ls-files *.cpp *.h *.lpp *.ypp *.def ':!third_party')
sed -i 's/#undef DIAGNOSTIC_KIND/#undef CARBON_DIAGNOSTIC_KIND/' toolchain/diagnostics/diagnostic_registry.def
```

Note this isn't *quite* everything, but it's intended to be a large pass at everything:

```
╚╡git grep '#define ' *.cpp *.h *.lpp *.ypp *.def ':!third_party' | grep -v '#define CARBON' | grep -v _H_
explorer/syntax/lexer.lpp:  #define YY_USER_ACTION                                             \
explorer/syntax/lexer.lpp:  #define SIMPLE_TOKEN(name) \
explorer/syntax/lexer.lpp:  #define ARG_TOKEN(name, arg) \
explorer/syntax/parse_and_lex_context.h:#define YY_DECL                                                         \
migrate_cpp/cpp_refactoring/var_decl.cpp:#define ABSTRACT_TYPE(Class, Base)
migrate_cpp/cpp_refactoring/var_decl.cpp:#define TYPE(Class, Base)     \
```

We may in particular want to do a pass to clean up #ifdef guards and make them be CARBON_ rooted.

explorer/interpreter/resolve_control_flow.cpp

@@ -78,10 +78,10 @@ static auto ResolveControlFlow(Nonnull<Statement*> statement,
       return Success();
     case StatementKind::If: {
       auto& if_stmt = cast<If>(*statement);
-      RETURN_IF_ERROR(
+      CARBON_RETURN_IF_ERROR(
           ResolveControlFlow(&if_stmt.then_block(), loop, function));
       if (if_stmt.else_block().has_value()) {
-        RETURN_IF_ERROR(
+        CARBON_RETURN_IF_ERROR(
             ResolveControlFlow(*if_stmt.else_block(), loop, function));
       }
       return Success();
@@ -89,25 +89,26 @@ static auto ResolveControlFlow(Nonnull<Statement*> statement,
     case StatementKind::Block: {
       auto& block = cast<Block>(*statement);
       for (auto* block_statement : block.statements()) {
-        RETURN_IF_ERROR(ResolveControlFlow(block_statement, loop, function));
+        CARBON_RETURN_IF_ERROR(
+            ResolveControlFlow(block_statement, loop, function));
       }
       return Success();
     }
     case StatementKind::While:
-      RETURN_IF_ERROR(ResolveControlFlow(&cast<While>(*statement).body(),
-                                         statement, function));
+      CARBON_RETURN_IF_ERROR(ResolveControlFlow(&cast<While>(*statement).body(),
+                                                statement, function));
       return Success();
     case StatementKind::Match: {
       auto& match = cast<Match>(*statement);
       for (Match::Clause& clause : match.clauses()) {
-        RETURN_IF_ERROR(
+        CARBON_RETURN_IF_ERROR(
             ResolveControlFlow(&clause.statement(), loop, function));
       }
       return Success();
     }
     case StatementKind::Continuation:
-      RETURN_IF_ERROR(ResolveControlFlow(&cast<Continuation>(*statement).body(),
-                                         std::nullopt, std::nullopt));
+      CARBON_RETURN_IF_ERROR(ResolveControlFlow(
+          &cast<Continuation>(*statement).body(), std::nullopt, std::nullopt));
       return Success();
     case StatementKind::ExpressionStatement:
     case StatementKind::Assign:
@@ -124,7 +125,7 @@ auto ResolveControlFlow(Nonnull<Declaration*> declaration) -> ErrorOr<Success> {
       auto& function = cast<FunctionDeclaration>(*declaration);
       if (function.body().has_value()) {
         FunctionData data = {.declaration = &function};
-        RETURN_IF_ERROR(
+        CARBON_RETURN_IF_ERROR(
             ResolveControlFlow(*function.body(), std::nullopt, &data));
       }
       break;
@@ -132,21 +133,21 @@ auto ResolveControlFlow(Nonnull<Declaration*> declaration) -> ErrorOr<Success> {
     case DeclarationKind::ClassDeclaration: {
       auto& class_decl = cast<ClassDeclaration>(*declaration);
       for (Nonnull<Declaration*> member : class_decl.members()) {
-        RETURN_IF_ERROR(ResolveControlFlow(member));
+        CARBON_RETURN_IF_ERROR(ResolveControlFlow(member));
       }
       break;
     }
     case DeclarationKind::InterfaceDeclaration: {
       auto& iface_decl = cast<InterfaceDeclaration>(*declaration);
       for (Nonnull<Declaration*> member : iface_decl.members()) {
-        RETURN_IF_ERROR(ResolveControlFlow(member));
+        CARBON_RETURN_IF_ERROR(ResolveControlFlow(member));
       }
       break;
     }
     case DeclarationKind::ImplDeclaration: {
       auto& impl_decl = cast<ImplDeclaration>(*declaration);
       for (Nonnull<Declaration*> member : impl_decl.members()) {
-        RETURN_IF_ERROR(ResolveControlFlow(member));
+        CARBON_RETURN_IF_ERROR(ResolveControlFlow(member));
       }
       break;
     }
@@ -161,7 +162,7 @@ auto ResolveControlFlow(Nonnull<Declaration*> declaration) -> ErrorOr<Success> {
 
 auto ResolveControlFlow(AST& ast) -> ErrorOr<Success> {
   for (auto declaration : ast.declarations) {
-    RETURN_IF_ERROR(ResolveControlFlow(declaration));
+    CARBON_RETURN_IF_ERROR(ResolveControlFlow(declaration));
   }
   return Success();
 }