[analysis_server_plugin] Give `AnalysisRule` access to `ResolvedLibraryResult`

[FMorschel]

Similar to https://github.com/dart-lang/sdk/issues/57092, I'm proposing we add a way for the ServerPlugin to access the whole ResolvedLibraryResult and not just the unit. This would allow us to handle the parts with the import feature, as well as some other local definitions.

Related CL https://dart-review.googlesource.com/c/sdk/+/456321