RFR: Merge openjdk/jdk:master

[William Kemper]

Pull in recent changes to control thread from upstream.

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Commit messages:
 - Merge openjdk/jdk:master
 - 8319578: Few java/lang/instrument ignore test.java.opts and accept test.vm.opts only
 - 8316460: 4 javax/management tests ignore VM flags
 - 8226919: attach in linux hangs due to permission denied accessing /proc/pid/root
 - 8325038: runtime/cds/appcds/ProhibitedPackage.java can fail with UseLargePages
 - 8325203: System.exit(0) kills the launched 3rd party application
 - 8325264: two compiler/intrinsics/float16 tests fail after JDK-8324724
 - 8325517: Shenandoah: Reduce unnecessary includes from shenandoahControlThread.cpp
 - 8325563: Remove unused Space::is_in
 - 8325551: Remove unused obj_is_alive and block_start in Space
 - ... and 23 more: https://git.openjdk.org/shenandoah/compare/710fde73...3e8868a4

The webrevs contain the adjustments done while merging with regards to each parent branch:
 - master: https://webrevs.openjdk.org/?repo=shenandoah&pr=393&range=00.0
 - openjdk/jdk:master: https://webrevs.openjdk.org/?repo=shenandoah&pr=393&range=00.1

Changes: https://git.openjdk.org/shenandoah/pull/393/files
  Stats: 3012 lines in 118 files changed: 2096 ins; 367 del; 549 mod
  Patch: https://git.openjdk.org/shenandoah/pull/393.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah.git pull/393/head:pull/393

PR: https://git.openjdk.org/shenandoah/pull/393