RFR: 8287805: Shenandoah: consolidate evacuate-update-root closures

[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

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Commit messages:
 - 8287805: Shenandoah: consolidate evacuate-update-root closures
 - Merge branch 'master' into consolidate_evac_root_closures
 - v0
 - v0

Changes: https://git.openjdk.java.net/jdk/pull/9023/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=9023&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8287805
  Stats: 70 lines in 4 files changed: 7 ins; 30 del; 33 mod
  Patch: https://git.openjdk.java.net/jdk/pull/9023.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/9023/head:pull/9023

PR: https://git.openjdk.java.net/jdk/pull/9023