RFR: 8287805: Shenandoah: consolidate evacuate-update-root closures [v6]

[Zhengyu Gu]

> ShenandoahEvacuateUpdateMetadataClosure and ShenandoahEvacuateUpdateRootsClosure are mostly same, can be consolidated.
> 
> Also, only uses of ShenandoahEvacuateUpdateMetadataClosure all pass MO_UNORDERED template parameter, so it can be eliminated.
> 
> Test:
> 
> - [x] hotspot_gc_shenandoah

Zhengyu Gu has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 13 additional commits since the last revision:

 - Merge branch 'master' into JDK-8287805-evac-updt-closures
 - Move get thread closer to the use
 - Aleksey's comment
 - Aleksey's comment
 - Merge branch 'master' into JDK-8287805-evac-updt-closures
 - v1
 - Remove unused impl
 - Review feedback
 - Merge branch 'master' into JDK-8287805-evac-updt-closures
 - 8287805: Shenandoah: consolidate evacuate-update-root closures
 - ... and 3 more: https://git.openjdk.org/jdk/compare/3fc125de...8c12588d

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/9023/files
  - new: https://git.openjdk.org/jdk/pull/9023/files/44f50839..8c12588d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9023&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9023&range=04-05

  Stats: 98651 lines in 2162 files changed: 52824 ins; 28883 del; 16944 mod
  Patch: https://git.openjdk.org/jdk/pull/9023.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9023/head:pull/9023

PR: https://git.openjdk.org/jdk/pull/9023