RFR: 8342444: Shenandoah: Uncommit regions from a separate, STS aware thread [v10]

[William Kemper]

> Currently, Shenandoah uncommits regions from its control thread. The control thread is responsible for starting GC cycles in a timely fashion. Uncommitting memory from this thread may introduce unwanted delays in the control thread's response to GC pressure.

William Kemper has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 21 commits:

 - Merge jdk/master
 - Use count of regions uncommitted to compute uncommit delta
 - Decouple polling interval from uncommit time out
 - Log uncommitted delta and capacity
 - Merge remote-tracking branch 'jdk/master' into shen-uncommit-thread
 - Restore logging format, show change in committed heap, rather than usage
 - Allow commits initially
 - Use idiomatic name for CADR class
 - Improve comments
 - Do not notify uncommit thread when uncommit is forbidden
 - ... and 11 more: https://git.openjdk.org/jdk/compare/05ee562a...e70d874e

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Changes: https://git.openjdk.org/jdk/pull/22019/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22019&range=09
  Stats: 514 lines in 9 files changed: 387 ins; 94 del; 33 mod
  Patch: https://git.openjdk.org/jdk/pull/22019.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22019/head:pull/22019

PR: https://git.openjdk.org/jdk/pull/22019