[clang] [Clang][AST] Track whether template template parameters used the 'typename' keyword (PR #88139)

[Krystian Stasiowski via cfe-commits]

sdkrystian wrote:

@erichkeane I added a release note. Regarding the addition of an enumeration type, how about:
```cpp
enum class TypeParmKeyword {
  Class,
  Typename
};
```

(I used `TypeParm` because a template template parameter is a _type-parameter_ in the C++ grammar, but I'm open to alternatives. Also, type template parameters can have no `class` or `typename` keyword, so should there also be an enumerator `None` to reflect this? Also also, should I change `TypeTemplateParmDecl` to use this enumeration type as well?)

https://github.com/llvm/llvm-project/pull/88139