LPS-46460 Extract MessageBoard usages to methods and add tests for them

https://issues.liferay.com/browse/LPS-46460
LPS-46460 Comments API: absorb MessageBoard usages from Blogs service

https://issues.liferay.com/browse/LPS-46460
LPS-46460 use the service reference you have
LPS-46460 this is really the MB impl of the comment manager API
LPS-46460 clean up old references
LPS-46460 REGENERATED
LPS-46460 The class under test was renamed, so rename the test as well

https://issues.liferay.com/browse/LPS-46460
LPS-46460 BlogsEntry local service: unit test with CommentManager now 

https://issues.liferay.com/browse/LPS-46460
LPS-46460 Linkback and Trackback tests: passing again

https://issues.liferay.com/browse/LPS-46460
LPS-46460 Remove SystemException from throws - no logic changes

https://issues.liferay.com/browse/LPS-46460
LPS-46460 The nullsafe case is important enough to deserve a top class

https://issues.liferay.com/browse/LPS-46460
LPS-46460 Unit test the generic, registry-driven CommentManager impl

https://issues.liferay.com/browse/LPS-46460
LPS-46460 SF
LPS-46460 Since this does nothing, no need to throw those
LPS-46460 See Dummy*.java
LPS-46460 addDiscussion pairs well with deleteDiscussion
LPS-46460 SF
LPS-46460 That is not a real interface
LPS-46460 SF
LPS-46460 Match CommentManagerImplTest#testAllCallsAreDelegated