RFR: 8328101: Parallel: Obsolete ParallelOldDeadWoodLimiterMean and ParallelOldDeadWoodLimiterStdDev [v2]

[Albert Mingkun Yang]

> Simple refactoring Parallel full-gc dead word calculation and removing two jvm flags.
> 
> Test: tier1-3

Albert Mingkun Yang has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains one commit:

  pgc-dead-ratio

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Changes: https://git.openjdk.org/jdk/pull/18278/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18278&range=01
  Stats: 244 lines in 7 files changed: 8 ins; 219 del; 17 mod
  Patch: https://git.openjdk.org/jdk/pull/18278.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18278/head:pull/18278

PR: https://git.openjdk.org/jdk/pull/18278