Rollup of 5 pull requests
Successful merges:
- #136293 (document capacity for ZST as example)
- #136359 (doc all differences of ptr:copy(_nonoverlapping) with memcpy and memmove)
- #136816 (refactor `notable_traits_button` to use iterator combinators instead of for loop)
- #138552 (Misc print request handling cleanups + a centralized test for print request stability gating)
- #138573 (Make `_Unwind_Action` a type alias, not enum)
r? `@ghost`
`@rustbot` modify labels: rollup
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