[NEXUS-5971] remove use of ExtensionPoint
Remove deprecated index related classes.
Moving compat to depend on core
Tearing down compat

Leaving events only for now
Merge remote-tracking branch 'origin/NEXUS-5971-remove-managed-extensionpoint' into remove-deprecated-classes
Events redirected.

This change affects only EventInspectors! All the other EventBus users
subscribers are still safe
Remove deprecated classes.
Remove nexus-compat module
Repository local storage improvements.

Changes:
* removed way too much java.io.File exists/mkdir/isXXX invocations
* relocated mkdir from core to FS LS (of repo baseDir)
* relocated when mkdir happens (only once, not per every getBaseDir invocation)
* repoBase dir is calculated and created only once, and is cached and reused
* improved/removed code duplication regarding storage contexts
Fixed Mocks in UTs
Reformat, no code change
Fixing logging, use slf4j api
NEXUS-6050: Improve logging
NEXUS-5998: no need to (re)fetch group membership unless using static mapping (because with dynamic mapping the membership details are already populated)
NEXUS-5998: short-circuit LDAP role-search if none of the roles exist in LDAP
Merge remote-tracking branch 'origin/master' into NEXUS-6050-improve-ar-logging
NEXUS-6050: More logging improvements

Using goodies ComponentSupport instead of the deprecated
AbstractLoggingComponent
NEXUS-6050: Expose proxy repo for subclasses
NEXUS-6050: Expose maven proxy and use it in logging
NEXUS-6050: Fixing NPE prone logging