Auto merge of #58608 - pnkfelix:warning-period-for-detecting-nested-impl-trait, r=zoxc
Warning period for detecting nested impl trait
Here is some proposed code for making a warning period for the new checking of nested impl trait.
It undoes some of the corrective effects of PR #57730, by using boolean flags to track parts of the analysis that were previously skipped prior to PRs #57730 and #57981 landing.
Cc #57979