RFR: 8244817: Add configuration logging similar to ZGCs to other GCs

[stefan.johansson at oracle.com]

Hi,

Please review this enhancement to improve startup logging for G1, 
Parallel and Serial.

Webrev: http://cr.openjdk.java.net/~sjohanss/8244817/00/
Issue: https://bugs.openjdk.java.net/browse/JDK-8244817

Summary
ZGC has some really nice initialization logging that really helps when 
analyzing multiple logs. It would be nice to have something similar in 
the other GCs. This change adds a InitLogger which can be used to print 
basic configuration that might be interesting to have in the GC logs. 
ZGC have some specific things in their logs and I've not included 
changing Z to make use of the new InitLogger, but this can be done as a 
follow up if it makes sense.

After some discussion with different people I decided to avoid adding to 
the CollectedHeap interface. Instead all GCs that make use of this 
should call the InitLogger in their initialization code.

There might be more information that make sense to put into to this 
block of logging and I plan to file a few follow-up. For example, to 
look at G1s perodic GC startup logging, but also to change the the 
compressed oops logging that become somewhat duplicated on info level 
after this change.

Testing
Mach5 1-3

Thanks,
Stefan