[clang] Include type specifiers in typo correction when checking isCXXDeclarationSpecifiers.

- add more tests (the test added in https://github.com/llvm/llvm-project/commit/2f448467e4254ddc3191136c968e6054bc009b88 is weak);
- improve the `MyTemplate<type_typo, int>();` case, with this patch, typo correction
  suggests the type decl, and no regressions found.

Differential Revision: https://reviews.llvm.org/D83025