Remove deprecated index related classes.
Moving compat to depend on core
Tearing down compat

Leaving events only for now
[NEXUS-5971] remove use of ExtensionPoint
Events redirected.

This change affects only EventInspectors! All the other EventBus users
subscribers are still safe
Remove deprecated classes.
Remove nexus-compat module
NEXUS-5971: drop custom guice-nexus scanning/binding code
NEXUS-5971: widen SimpleRepositoryImpl binding so it can be seen by the mediator (could also have added Repository.class to @Typed)
NEXUS-5971: prefer non-group repositories over group repositories (as some repositories like P2 use the same hint for both non-group and group repositories and don't restrict visibility with @Typed)