Rollup merge of #33852 - arielb1:autoderef-iterator, r=eddyb

refactor autoderef to avoid prematurely registering obligations

Refactor `FnCtxt::autoderef` to use an external iterator and to not
register any obligation from the main autoderef loop, but rather to
register them after (and if) the loop successfully completes.

Fixes #24819
Fixes #25801
Fixes #27631
Fixes #31258
Fixes #31964
Fixes #32320
Fixes #33515
Fixes #33755

r? @eddyb