[11] Pick up jdk-11.0.9+2 to sh/jdk11

[Aleksey Shipilev]

Upstream had published jdk-11.0.9+2. This brings the huge Shenandoah integration.

The merge is tedious, but simple. The leftover differences against upstream are:
  https://cr.openjdk.java.net/~shade/shenandoah/merges/jdk11-11.0.9%2b2-leftovers/webrev.01/

Testing: hotspot_gc_shenandoah {fastdebug,release}

-- 
Thanks,
-Aleksey