Generational ZGC Early Access builds 3

[Stefan Karlsson]

Hi all,

We've now published new Generational ZGC Early Access builds on:
https://jdk.java.net/genzgc

Changes since previous EA builds:

Rebased on top of jdk-20+21

Added macOS builds

Rewrote heuristics to deal with a problematic case where Generational 
ZGC spent too much focus on doing young generation collection when it's 
more beneficial to spend resources to collect the old generation.

Rewrote GC logging to easier see what log lines belong to what 
collection / generation. Plus a bunch of other changes to hopefully make 
it easier to read and understand the GC logs.

Enhanced the barrier elision to remove barriers from array access of 
newly allocated arrays.

Enhanced the generated hs_err crash text file

Fixed and unified code quality and style.

Thanks,
StefanK