NEXUS-6323: Plexus cipher reimplementation

Adding a re-implementation of PlexusCipher that uses CryptoHelper.

Issue
https://issues.sonatype.org/browse/NEXUS-6323

CI
NA
The two subclasses have different injected constructor parameters, so while the base is the same they're configured differently (see PasswordCipherMavenLegacyImpl vs PasswordCipherMavenImpl which setup different algorithms).