[clang] [clang-format] Add ClassHeadName to help annotating StartOfName (PR #124891)

[Owen Pan via cfe-commits]

================
@@ -1146,6 +1175,8 @@ TEST_F(TokenAnnotatorTest, UnderstandsRequiresClausesAndConcepts) {
   EXPECT_TOKEN(Tokens[31], tok::greater, TT_TemplateCloser);
   EXPECT_EQ(Tokens[31]->FakeRParens, 1u);
   EXPECT_TRUE(Tokens[31]->ClosesRequiresClause);
+  // FIXME:
+  // EXPECT_TOKEN(Tokens[33], tok::identifier, TT_Unknown); // Not ClassHeadName
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owenca wrote:

```suggestion
  // FIXME:
  // EXPECT_TOKEN(Tokens[33], tok::identifier, TT_Unknown); // Not TrailingAnnotation
```

https://github.com/llvm/llvm-project/pull/124891