[`peft`] Support key_mapping with PEFT models (#46766)
* Support key_mapping with PEFT models
* Simplify test using uploaded tiny-random PEFT adapter
* Add extra edge case test
* Use a tmp_cache to avoid the potentially read-only default CI cache dir
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Co-authored-by: Anton Vlasjuk <73884904+vasqu@users.noreply.github.com>
