[11] RFR: Pick up 11.0.7+3 to sh/jdk11

[Aleksey Shipilev]

Upstream published 11.0.7+3 tag. Let's pick it up to sh/jdk11.

The merge is not trivial, but simple enough. Changeset list:
  https://cr.openjdk.java.net/~shade/shenandoah/merges/jdk11-11.0.7%2b3/changesets.txt

Merge changeset:
  https://cr.openjdk.java.net/~shade/shenandoah/merges/jdk11-11.0.7%2b3/merge.changeset

Testing: hotspot_gc_shenandoah {fastdebug,release}

-- 
Thanks,
-Aleksey