* Also does this for `absl::internal::identity_t` which is now `absl::internal::type_identity_t`
* This is clearer naming as this is a backfill of `std::type_identity` (the identity type), and not `std::identity` (the identity function)

PiperOrigin-RevId: 594316002
Change-Id: I5fb8cf7e3d07c1bc736cbecd202e7d556b6ea33e