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Rollup merge of #156222 - cammeresi:20260505-ro-mod, r=Mark-Simulacrum
Stabilize `Result::map_or_default` and `Option::map_or_default`
Tracking issue: rust-lang/rust#138099
FCP completed: https://github.com/rust-lang/rust/issues/138099#issuecomment-4184062429
Closes: rust-lang/rust#138099
