RFR: 8287805: Shenandoah: consolidate evacuate-update-root closures [v2]

[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 six additional commits since the last revision:

 - 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/c3a41277..427c3a45

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9023&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9023&range=00-01

  Stats: 64291 lines in 1573 files changed: 35441 ins; 15195 del; 13655 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