[clang] [llvm] Finish deleting the le32/le64 targets (PR #98497)

[Fangrui Song via cfe-commits]

MaskRay wrote:

It seems that Halide (https://github.com/halide/Halide/pull/5934), an important user, still needs generic 32-bit 64-bit Clang targets.
The removed le32/le64 targets fulfilled this need.
(This change broke my internal users. Sorry that I did not realize that Halide#5934 was closed without an actual fix @abadams).

@AaronBallman Are you comfortable with bring back le32/le64 temporarily?
The few occurrences in `bitfield-*` don't serve useful testing purposes, and they can be removed if they feel like eyesore.


https://github.com/llvm/llvm-project/pull/98497