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

[Aleksey Shipilev]

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}

-- 
Thanks,
-Aleksey