Fix issue with GeneratedValue in PfGeneratedIdKey

Fix issue with  GeneratedValue in PfGeneratedIdKey

PfGeneratedIdKey class (which is used as a composite key
in JpaPolicyAudit and JpaPdpStatistics) uses GeneratedValue
in a wrong way and not according to the specification.
This review fixes it. PfGeneratedIdKey class is removed, and the
generatedId is directly specified in the JpaPolicyAudit and
JpaPdpStatistics classes.

Note: These classes are only used by PAP, so the related methods for db
interaction is removed as PAP directly talks to DB using spring
repository layer. Also the only end result this change brings is that the
'generatedId' alone will be used as the primary key instead of
'generatedId, name and version' together.

Corresponding changes in
DB Migrator: https://gerrit.onap.org/r/c/policy/docker/+/127139
PAP: https://gerrit.onap.org/r/c/policy/pap/+/127130

Change-Id: Ib4ea8b60ffe5c2480746569c0354bf474a6b7006
Issue-ID: POLICY-3897
Signed-off-by: a.sreekumar <ajith.sreekumar@bell.ca>