RFR: 8245724: Move g1 periodic gc logging to G1InitLogger

[Kim Barrett]

> On May 26, 2020, at 8:28 AM, stefan.johansson at oracle.com wrote:
> 
> Hi,
> 
> Please review this change to move more G1 logging to gc+init.
> 
> Webrev: http://cr.openjdk.java.net/~sjohanss/8245724/00/
> JBS: https://bugs.openjdk.java.net/browse/JDK-8245724
> 
> Summary
> The initial periodic GC logs are good candidates for being part of the G1InitLogger so I moved them there. Since this logging doesn't really fit in any of the existing categories I added print_gc_specific() to the InitLogger so that the GCs that want to add more stuff have a good place to put it.
> 
> Testing
> Mach5 tier1-2 and local verification.
> 
> Thanks,
> Stefan

Looks good.