[8] 2020-03-02, Bulk backports to sh/jdk8

[Aleksey Shipilev]

This backports a round of relatively safe changes for 8u:
  [backport] 8240070: Shenandoah: remove obsolete ShenandoahCommonGCStateLoads
  [backport] 8239868: Shenandoah: ditch C2 node limit adjustments
  [backport] 8239904: Shenandoah: accumulated penalties should not be over 100% of capacity
  [backport] 8240069: Shenandoah: turn more flags diagnostic
  [backport] 8240076: Shenandoah: pacer should cover reset and preclean phases
  [backport] 8240215: Shenandoah: remove ShenandoahAllocationTrace

8u webrev:
  https://cr.openjdk.java.net/~shade/shenandoah/backports/jdk8u-20200302/

Testing: hotspot_gc_shenandoah {fastdebug,release}

-- 
Thanks,
-Aleksey