RFR: 8344197: SM cleanup in java.util.concurrent

[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.

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Commit messages:
 - Drop mention of permissions
 - 8344197: SM cleanup in java.util.concurrent

Changes: https://git.openjdk.org/jdk/pull/22119/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22119&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8344197
  Stats: 365 lines in 14 files changed: 7 ins; 317 del; 41 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