RFR: 8287805: Shenandoah: consolidate evacuate-update-root closures [v4]

[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 10 additional commits since the last revision:

 - 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
 - Merge branch 'master' into consolidate_evac_root_closures
 - v0
 - v0

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/9023/files
  - new: https://git.openjdk.org/jdk/pull/9023/files/689335bf..f076e810

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9023&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9023&range=02-03

  Stats: 26049 lines in 302 files changed: 23432 ins; 1854 del; 763 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