[clang] [Clang][NFC] Remove TemplateArgumentList::OnStack (PR #79760)

[Krystian Stasiowski via cfe-commits]

sdkrystian wrote:

@erichkeane How does this sound?
> Removed support for constructing on-stack `TemplateArgumentList`s; interfaces should instead use `ArrayRef<TemplateArgument>` to pass template arguments. This reduces AST memory usage by 0.4% when compiling clang.



https://github.com/llvm/llvm-project/pull/79760