Rollup merge of #141076 - the8472:fix-zip-panic-safety2, r=workingjubilee

fix Zip unsoundness (again)

Some history: The Zip TrustedRandomAccess specialization has tried to emulate the side-effects of the naive implementation for a long time, including backwards iteration. #82292 tried to fix unsoundness (#82291) in that side-effect-preservation code, but this introduced some panic-safety unsoundness (#86443), but the fix #86452 didn't fix it for nested Zip iterators (#137255).

Rather than piling yet another fix ontop of this heap of fixes this PR reduces the number of cases in which side-effects will be preserved; the necessary API guarantee change was approved in #83791 but we haven't made use of that so far.

fixes #137255

Author: matthiaskrgr