Avoid calling Title::makeTitleSafe in User::idFromName

We don't want to call Title::makeTitleSafe yet, since that call path
ends up needing the user language, which ends up trying to load the
user object, which ends up back in User::idFromName.

Bug: 54193
Change-Id: I05aacd30be66fe505b5c211113ea938fa82e2492