NEXUS-7769: Step 1: Implode LDAP plugin

As when we merged LDAP OSS and Pro, we left all the packages
and code mainly untouched with a lot of redundancy.

Changes:
* removed OSS config, hence OSS-Pro upgrade step too
* only Pro modello left in place for now
* removed unused and redunant classes
NEXUS-7769: Update configs
NEXUS-7769: Update license exclusion of moved file
NEXUS-7769: Up IT related configs
NEXUS-7769: IT related fixes

As pw encoding is now not using legacy anymore, and Realm name
changed.
NEXUS-7769: Do not expose more than needed

Almost all of the plugin moved into internal package
NEXUS-7769: Update license exclusion
NEXUS-7769: Moved everything into internal

As nothing is actually used outside of the plugin
Merge pull request #919 from sonatype/NEXUS-7769-implode-ldap

NEXUS-7769: Step 1: Implode LDAP plugin