RFR: 8230431: Move G1 trace code from gcTrace* to G1 directory

[Kim Barrett]

> On Sep 2, 2019, at 2:53 PM, Stefan Johansson <stefan.johansson at oracle.com> wrote:
> 
> Hi all,
> 
> Please review this cleanup to prepare for fixing JDK-8209802.
> 
> JBS: https://bugs.openjdk.java.net/browse/JDK-8230431
> Webrev: http://cr.openjdk.java.net/~sjohanss/8230431/00/
> 
> Summary:
> Currently a lot of JFR related gc code is located in share/gcTrace.* and share/gcTraceSend.cpp. To fix JDK-8209802, we need to have a way to initialize and register a few JFR constants specific to G1 and to prepare for this I suggest that we move the G1 parts from the above files into g1/g1Trace.* to create a place where this can be done. This is something that probably should have been done regardless of this bug, but now is a good to get it done. 
> 
> Testing:
> Mach5 tier 1-3
> 
> Cheers,
> Stefan

Looks good.