RFR: 8291037: Move PLAB resizing mechanism to G1EvacStats [v3]

[Thomas Schatzl]

> Hi all,
> 
>   please review this refactoring that moves the PLAB resizing mechanism to `G1EvacStats` as G1 is the only user for this functionality.
> 
> The change is split into two commits for easier review: 65eef6482cc0a995d29e822c9c26063bb42c7679 only moves the code,  028e3adeca1d496520f0c79f3b4bcedd7e7f0f15 tries to improve it a bit. 
> 
> Note that this change also removes the old, unused PLAB re-sizing algorithm previously used by CMS, hence the relatively large count of deleted LOC.
> 
> Testing: gha, gc/g1
> 
> Thanks,
>   Thomas

Thomas Schatzl has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains four commits:

 - Merge branch 'master' into 8291037-move-resizeplab-code
 - improve one comment
 - touch-up
 - Code motion

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

Changes: https://git.openjdk.org/jdk/pull/9644/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9644&range=02
  Stats: 186 lines in 6 files changed: 67 ins; 100 del; 19 mod
  Patch: https://git.openjdk.org/jdk/pull/9644.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9644/head:pull/9644

PR: https://git.openjdk.org/jdk/pull/9644