[clang][AST] fix lack comparison of declRefExpr in ASTStructuralEquivalence

[mzyKi]

Fixes #66047
Before fix,the following testcase expected true. While I think only comparison of declName is not sufficient.Thanks for giving suggestions.

TEST_F(StructuralEquivalenceStmtTest, DeclRefENoEq) {
  std::string Prefix = "enum Test { AAA, BBB };";
  auto t = makeStmts(
      Prefix + "void foo(int i) {if (i > 0) {i = AAA;} else {i = BBB;}}",
      Prefix + "void foo(int i) {if (i > 0) {i = BBB;} else {i = AAA;}}",
      Lang_CXX03, ifStmt());
  EXPECT_FALSE(testStructuralMatch(t)); // EXPECT_TRUE
}

[cor3ntin]

Thanks for working on that!
Can you explain why you are comparing declaration only with their name? that seems suspicious to me. Otherwise, I think the intent of the change is correct

[cor3ntin]

You should edit clang/docs/ReleaseNotes.rst, indicating that #66047 was fixed,
and edit the description of the PR with Fixes #66047 so that it gets closed automatically.

Otherwise LGTM

[danix800]

LGTM! If no further comment I'll merge this in a day or two.