Adding `ResolvedLibraryResult` and `ResolvedUnitResult` to all our `RefactoringImpl` classes

[FMorschel]

Based on #57092, I'm proposing we also add both ResolvedLibraryResult and ResolvedUnitResult to all our RefactoringImpl classes.

This will help us with some processing without the need to use the SearchEngine for some easier refactorings (like #57031). And since for most of the current Refactors we already provide a ResolvedUnitResult, we already have the ResolvedLibraryResult handy.

I've opened https://dart-review.googlesource.com/c/sdk/+/453845 for this change.

I'll add you, @srawlins and @bwilkerson as reviewers. Tagging you both here so we can discuss this (if you disagree for any reason).