RFR: 8344197: SM cleanup in java.util.concurrent [v2]

[Roger Riggs]

> Refactored to remove use of doPrivileged() and use of SecurityManager.
> The DefaultForkJoinWorkerThreadFactory no longer uses the SM to target a common thread pool.
> 
> A careful review is requested.

Roger Riggs has updated the pull request incrementally with one additional commit since the last revision:

  Revert all changes to ForkJoinPool; defer remove of SM use
  Addressed other review comments

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Changes:
  - all: https://git.openjdk.org/jdk/pull/22119/files
  - new: https://git.openjdk.org/jdk/pull/22119/files/cd90f45f..21013c28

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=22119&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=22119&range=00-01

  Stats: 124 lines in 6 files changed: 103 ins; 11 del; 10 mod
  Patch: https://git.openjdk.org/jdk/pull/22119.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22119/head:pull/22119

PR: https://git.openjdk.org/jdk/pull/22119