Rollup merge of #137298 - compiler-errors:mir-wf, r=lcnr

Check signature WF when lowering MIR body

Alternative to #137233.

rust-lang/rust#137233 (comment)

Fixes rust-lang/rust#137186

We do this check in `mir_drops_elaborated_and_const_checked` and not during `mir_promoted` because that may result in borrowck cycles if WF requires looking into an opaque hidden type. This causes some TAIT tests to fail unnecessarily.

r? lcnr

try-job: test-various