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

[Krystian Stasiowski via cfe-commits]

sdkrystian wrote:

@erichkeane I'm thinking of keeping the use of `bool` to represent the presence of `typename` in this patch, and opening another PR that changes both `TemplateTemplateParmDecl` and `TypeTemplateParmDecl` to use `TypeParmKeyword`... What do you think?

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