Auto merge of #66385 - ecstatic-morse:check-only-pass2, r=eddyb

Make dataflow-based const qualification the canonical one

For over a month, dataflow-based const qualification has been running in parallel with `qualify_consts` to check the bodies of `const` and `static`s. This PR removes the old qualification pass completely in favor of the dataflow-based one.

**edit:**
This PR also stops checking `QUALIF_ERROR_BIT` during promotion. This check appears to no longer serve a purpose now that the CTFE engine is more robust.

As a side-effect, this resolves #66167.

r? @eddyb

diff --cc src/librustc/mir/mod.rs
Simple merge