RFC: Pick up 11.0.7+1 to sh/jdk11

[Aleksey Shipilev]

Upstream published 11.0.7+1 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%2b1/changesets.txt

Merge changeset is way too large to be useful. So we would wait for builds to complete after this
push, and then tag the result shenandoah-jdk-11.0.7+1.

Testing: hotspot_gc_shenandoah {fastdebug,release}

-- 
Thanks,
-Aleksey