[Clang] Provide a type trait for implicit lifetime types (P2674)

[cor3ntin]

To implement P2674R1
https://wg21.link/P2674R1 which does require some compiler magic

[llvmbot]

@llvm/issue-subscribers-c-1

Author: cor3ntin (cor3ntin)

To implement P2674R1 https://wg21.link/P2674R1 which does require some compiler magic

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: cor3ntin (cor3ntin)

To implement P2674R1 https://wg21.link/P2674R1 which does require some compiler magic