Implement MessageFactory-namespaced logger registry

[vy]

Fixes #2933 by deprecating AbstractLogger.checkMessageFactory() and removing its usages.

Rationale

In its current state, all LoggerContext#getLogger(String, MessageFactory) methods of all LoggerContext implementations delegate to LoggerRegistry, which in essence is a Map<MessageFactory, Map<String, Logger>>. That is, all LoggerRegistry-produced Loggers are MessageFactory-namespaced. This renders the checkMessageFactory() check redundant.

Put another way, getLogger("foo", someMF) will create a Logger associated with someMF. getLogger("foo") will create a Logger associated with the MF configured for the LC. In either case, if someMF != the MF configured for the LC, Loggers will differ anyway, hence checkMessageFactory() will always succeed.

[vy]

@rgoers, would you mind reviewing this, please? (Checked with @ppkarwasz, he also agrees with deprecating checkMF().)

[ppkarwasz]

Nice work Volkan!

This might be great for 2.25.0, but I am not sure the problem requires such a drastical changes. By this I mean the deprecations in LoggerRegistry.

Note also that all message factories should implement equals and hashCode (I think this is technically a minor version change).

[vy]

This might be great for 2.25.0, but I am not sure the problem requires such a drastical changes. By this I mean the deprecations in LoggerRegistry.

I will merge these changes to 2.x (targeting 2.25.0) and then cherry-pick these to 2.24.x without deprecation changes.

Note also that all message factories should implement equals and hashCode (I think this is technically a minor version change).

AFAICT, LocalizedMessageFactory is the only stateful MF; implemented equals() and hashCode() for it in c747f4f.