Revert "Add type avoidance to inferred MT bound lubbing"

[WojciechMazur]

This partially reverts #22142 from Scala 3.6.4

Withdraws regressions observed in #22661 until proper fix would be available in 3.7

[WojciechMazur]

@dwijnand @sjrd @odersky @Gedochao

Anyone against this change to release 3.6.4? We were not able to find a proper fix before the cutoff for backports, so we'd like to give us more time so it can be fixed in 3.7.
This PR does not revert whole PR, but only a single commit.
After testing with OpenCB (with addition of changes from #22653) we have not found any new regressions and were able to make the project compile. However, based on discussion it might not be obvious if the old behaviour should be restored or not. #22661 (comment)
Even if we decide that new behaviour should stay in 3.7, I personally believe that we should preserve the old behaviour for the last 3.6 release.

[smarter]

Before this was fixed, I observed compiler crashes in pickling due to local symbols escaping, reverting this is likely to reintroduce these crashes.

[sjrd]

The fix here was fixing a very obvious and serious problem with type variables used outside of their defining scope. I don't think reverting is a good idea.

[dwijnand]

Yeah, we shouldn't revert this.