[11] RFR/RFC: Pick up 11.0.6+1 to sh/jdk11

[Roman Kennke]

OK. Let's do it.

Roman


> 11u updates project had tagged the 11.0.6+1, which includes lots of outstanding changes in 11u
> project. Let's pick those up.
> 
> I believe I did the merge right, but there are generally awkward things that might need follow-ups.
> Notably, new CAS matchers in aarch64.ad and BSC2::clone_barrier hooks. This would become more clear
> after we push and look through build/test/webrev results.
> 
> Changeset list:
>   https://cr.openjdk.java.net/~shade/shenandoah/merges/jdk11-11.0.6%2b1/changesets.txt
> 
> Merge changeset (large):
>   http://cr.openjdk.java.net/~shade/shenandoah/merges/jdk11-11.0.6%2b1/merge.changeset
> 
> Testing: hotspot_gc_shenandoah {fastdebug,release}
>