[5.7] Cherry pick a RegexBuilder and StringProcessing change#534

Merged

hamishknight merged 3 commits intoswiftlang:swift/release/5.7from

hamishknight:more-5.7-cherry-picks

Jul 1, 2022

Commits on Jul 1, 2022

Make unary builder return `Regex` type consistently.

rxwei
authored and
hamishknight
committed
Keep substring bounds when searching in Regex.wholeMatch

natecook1000
authored and
hamishknight
committed
Remove outdated comment
hamishknight
committed