RFR: 8191564: Refactor GC related servicability code into GC specific subclasses

[Roman Kennke]

> Currently, there's lots of GC specific code sprinkled over 
> src/hotspot/share/services. This change introduces a GC interface for 
> that, and moves all GC specific code to their respective 
> src/hotspot/share/gc directory.
> 
> http://cr.openjdk.java.net/~rkennke/8191564/webrev.00/ 
> <http://cr.openjdk.java.net/%7Erkennke/8191564/webrev.00/>
> 
> Testing: hotspot_gc and hotspot_serviceability, none showed regressions
> 
> Built minimal and server without regressions
> 
> What do you think?
> 

Ping?

Roman