RFR: 8287805: Shenandoah: consolidate evacuate-update-root closures [v3]

[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 incrementally with one additional commit since the last revision:

  Remove unused impl

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/9023/files
  - new: https://git.openjdk.org/jdk/pull/9023/files/427c3a45..689335bf

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9023&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9023&range=01-02

  Stats: 11 lines in 2 files changed: 0 ins; 11 del; 0 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