[clang-format] FIX: Misannotation 'auto' as trailing return type in lambdas

Lambdas with trailing return type 'auto' are annotated incorrectly. It causes a misformatting. The simpliest code to reproduce is:

```
auto list = {[]() -> auto { return 0; }};
```

Fixes #54798

Reviewed By: HazardyKnusperkeks, owenpan, curdeius

Differential Revision: https://reviews.llvm.org/D130299

Author: denis-fatkulin

clang/lib/Format/UnwrappedLineParser.cpp

@@ -2108,6 +2108,7 @@ bool UnwrappedLineParser::tryToParseLambda() {
     case tok::l_square:
       parseSquare();
       break;
+    case tok::kw_auto:
     case tok::kw_class:
     case tok::kw_template:
     case tok::kw_typename:

clang/unittests/Format/TokenAnnotatorTest.cpp

@@ -747,6 +747,21 @@ TEST_F(TokenAnnotatorTest, UnderstandsLambdas) {
   ASSERT_EQ(Tokens.size(), 8u) << Tokens;
   EXPECT_TOKEN(Tokens[0], tok::l_square, TT_LambdaLSquare);
   EXPECT_TOKEN(Tokens[5], tok::l_brace, TT_LambdaLBrace);
+
+  Tokens = annotate("[]() -> auto {}");
+  ASSERT_EQ(Tokens.size(), 9u) << Tokens;
+  EXPECT_TOKEN(Tokens[4], tok::arrow, TT_LambdaArrow);
+  EXPECT_TOKEN(Tokens[6], tok::l_brace, TT_LambdaLBrace);
+
+  Tokens = annotate("[]() -> auto & {}");
+  ASSERT_EQ(Tokens.size(), 10u) << Tokens;
+  EXPECT_TOKEN(Tokens[4], tok::arrow, TT_LambdaArrow);
+  EXPECT_TOKEN(Tokens[7], tok::l_brace, TT_LambdaLBrace);
+
+  Tokens = annotate("[]() -> auto * {}");
+  ASSERT_EQ(Tokens.size(), 10u) << Tokens;
+  EXPECT_TOKEN(Tokens[4], tok::arrow, TT_LambdaArrow);
+  EXPECT_TOKEN(Tokens[7], tok::l_brace, TT_LambdaLBrace);
 }
 
 } // namespace