[11] Bulk backports to sh/jdk11

[Aleksey Shipilev]

https://cr.openjdk.java.net/~shade/shenandoah/backports/jdk11-20200206/webrev.01/

This batch backports these simple fixes:
 [backport] 8237570: Shenandoah: cleanup uses of allocation/free threshold in static heuristics
 [backport] 8237586: Shenandoah: provide option to disable periodic GC
 [backport] 8238153: CTW: C2 (Shenandoah) compilation fails with "Unknown node in get_load_addr:
CreateEx"
 [backport] 8237038: Shenandoah: Reduce thread pool size in TestEvilSyncBug.java test
 [backport] 8233850: Shenandoah: Shenandoah thread count ergonomics should be container aware
 [backport] 8236851: Shenandoah: More details in Traversal GC event messages

All apply cleanly.

Testing: hotspot_gc_shenandoah {fastdebug, release}

-- 
Thanks,
-Aleksey