RFR: 8262885: Shenandoah: FullGC prologue does not need to save/restore heap has_forwarded_object flag [v2]

[Zhengyu Gu]

> Another trivial cleanup. FullGC prologue code does not change heap's has_forwarded_objects flag, there is no point to save/restore it.
> 
> Test:
> - [x] hotspot_gc_shenandoah

Zhengyu Gu has updated the pull request incrementally with three additional commits since the last revision:

 - Aleksey's comment
 - Removed whitespaces
 - Aleksey's comment

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/2797/files
  - new: https://git.openjdk.java.net/jdk/pull/2797/files/26b8b6d3..72eb25c5

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=2797&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=2797&range=00-01

  Stats: 6 lines in 1 file changed: 5 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2797.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2797/head:pull/2797

PR: https://git.openjdk.java.net/jdk/pull/2797