When inlining a function using the Mir inliner, we shouldn't rerun the
various Mir passes on it because the Mir has already been lowered and
that wil break various early Mir passes.

The issue in rust-lang#50411 is that we've inlined a function with promotions
whose Mir has already been lowered. The promotions are then copied into
the local function and we begin to run passes on their lowered Mir
which causes the ICE.

Fixes rust-lang#50411

This can be obtained via the `$mir_phase` value.

As suggested in the feedback for rust-lang#55244.

When I replaced the macro with a function, rustc started complaining
that there were two unused functions so I also removed those.