RFR: 8246134: ZGC: Restructure hs_err sections

[Stefan Karlsson]

Hi all,

Please review this small patch to restructure and cleanup the 
information ZGC prints to hs_err files (and jcmd VM.info).

https://cr.openjdk.java.net/~stefank/8246134/webrev.01/
https://bugs.openjdk.java.net/browse/JDK-8246134

The patch:
- Moves the Page Table dumping later, to make it easier to find the 
other sections
- Pretty print some info
- Add barrier set print (mostly to get rid of awkward double new lines)
- Update titles and cleanup newlines

Thanks,
StefanK