RFR/RFC: Pick up jdk-13+21+ to sh/jdk

[Aleksey Shipilev]

We have caught the moment in jdk/jdk where it is not broken anywhere. Let's pick that up. There is a
trivial merge required after ShRootProcessor changes.

Changesets:
  http://cr.openjdk.java.net/~shade/shenandoah/merges/jdk-13%2b21-plus/changesets.txt

Webrev (only "shenandoah" parts, since there is a huge Graal update):
  http://cr.openjdk.java.net/~shade/shenandoah/merges/jdk-13%2b21-plus/webrev.01/

Testing: hotspot_gc_shenandoah {fastdebug|release}, eyeballing webrev

-- 
Thanks,
-Aleksey