Rollup merge of #141659 - tkr-sh:map-or-default, r=Amanieu

Add `Result::map_or_default` and `Option::map_or_default`

Closes: rust-lang/rust#138068

_This PR has been recreated because of the inactivity of the author (Cf. rust-lang/rust#138068 (comment)

Author: tgross35