Only use implied bounds hack if bevy, and use deeply normalize in implied bounds hack
Consolidates the implied bounds computation mode into a single function, which deeply normalizes, and if it's in **compat** mode (for bevy), it extracts outlives bounds from the infcx.
Previously, we were using the implied bounds compat mode in two cases:
1. During WF, if it detects `ParamSet`
2. EVERYWHERE ELSE (lol) -- e.g. borrowck, predicate entailment, etc.
While I think this is fine, and the net effect was just that we emitted fewer diagnostics, it makes me uncomfortable that all crates were using the supposed "compat" code.
Fixes#137767
6c60abf51a