RFR: 8333825: GenShen: Revert/Remove ShenandoahMaxEvacLABRatio

[Y. Srinivas Ramakrishna]

ShenandoahMaxEvacLABRatio was intended as an experimental/research option and guardrail to manually bound the ceiling of PLABs used in Shenandoah and GenShen at the time that GenShen's LAB auto-sizing and allocation heuristics were somewhat nascent and immature. There is however a natural upper-bound of the heap region size for these local allocation buffers which prevent runaway growth, and the manual throttle has never had to be used, and the option thus appears somewhat vestigial. Removing it also reduces differences with upstream Shenandoah which should simplify GenShen's upstreaming reviews.

- Removed the option and its uses in Shen and GenShen code
- Adjusted logging to be consistent, and adjusted some comments in GenShen
- Tested with codepipeline, GC tests, and exercised the new log lines

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Commit messages:
 - Cosmetic change to debug level log.
 - Try and minimize changes wrt jdk tip.
 - Remove vestigial option ShenandoahMaxEvacLABRatio; move and adjust debug

Changes: https://git.openjdk.org/shenandoah/pull/446/files
  Webrev: https://webrevs.openjdk.org/?repo=shenandoah&pr=446&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8333825
  Stats: 53 lines in 3 files changed: 7 ins; 36 del; 10 mod
  Patch: https://git.openjdk.org/shenandoah/pull/446.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah.git pull/446/head:pull/446

PR: https://git.openjdk.org/shenandoah/pull/446