Make two transmute-related MIR lints into HIR lint
Make `PTR_TO_INTEGER_TRANSMUTE_IN_CONSTS` (rust-lang/rust#130540) and `UNNECESSARY_TRANSMUTES` (rust-lang/rust#136083) into "normal" HIR-based lints.
Funny enough this came up in the review of the latter (https://github.com/rust-lang/rust/pull/136083#issuecomment-2614301413), but I guess it just was overlooked.
But anywyas, there's no reason for these to be MIR lints; in fact, it makes the suggestions for them a bit more complicated than necessary.
Note that there's probably a few more simplifications and improvements to be done here. Follow-ups can be done in a separate PR, especially if they're about the messaging and suggestions themselves, which I didn't write.
e0278ed5af