RFR: 8205405: ZGC: Decouple JFR type registration

[Stefan Karlsson]

Looks good.

StefanK

On 2018-06-20 11:27, Per Liden wrote:
> When JDK-8205053 is completed, it becomes possible to register 
> subsystem-specific JFR types from outside of JFR. The code that 
> registers ZGC's two types is currently embedded into JFR itself. This 
> code can now be moved into ZGC itself.
> 
> Bug: https://bugs.openjdk.java.net/browse/JDK-8205405
> Webrev: http://cr.openjdk.java.net/~pliden/8205405/webrev.0
> 
> Testing: Manually generated and verified a test recording
> 
> /Per