RFR: Merge openjdk/jdk:master

[William Kemper]

This pulls in the latest upstream commits from tip. There was a [small change](https://github.com/openjdk/shenandoah/pull/154/commits/f7a1353f7bff269f8bd2750bc60af85fb04f4eed) to handle notifications of mark start and mark end to make Loom aware of old generation marking.

-------------

Commit messages:
 - Merge branch 'shenandoah-master' into upstream-merge-test
 - Merge branch 'shenandoah-master' into upstream-merge-test
 - Do not 'end mark' if old marking is in progress
 - Merge branch 'openjdk-mainline' into upstream-merge-test
 - 8291048: x86: compiler/c2/irTests/TestAutoVectorization2DArray.java fails with lower SSE
 - 8290848: LoadLibraryUnload.java still fails with "Too few cleared WeakReferences"
 - Merge
 - 8291006: java/foreign/TestUnsupportedPlatform fails after JDK-8290455
 - 8290455: jck test api/java_lang/foreign/VaList/Empty.html fails on some platforms
 - 8290460: Alpine: disable some panama tests that rely on std::thread
 - ... and 2218 more: https://git.openjdk.org/shenandoah/compare/16a9ab63...32991b5f

The webrevs contain the adjustments done while merging with regards to each parent branch:
 - master: https://webrevs.openjdk.org/?repo=shenandoah&pr=154&range=00.0
 - openjdk/jdk:master: https://webrevs.openjdk.org/?repo=shenandoah&pr=154&range=00.1

Changes: https://git.openjdk.org/shenandoah/pull/154/files
  Stats: 1034164 lines in 11702 files changed: 672855 ins; 251524 del; 109785 mod
  Patch: https://git.openjdk.org/shenandoah/pull/154.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah pull/154/head:pull/154

PR: https://git.openjdk.org/shenandoah/pull/154