[jdk11u-dev] RFR: 8221351: Crash in KlassFactory::check_shared_class_file_load_hook

[Joshua Cao]

This fixes a crash in JDK 11.

Merge conflicts are mostly trivial. We can keep hunks from both HEAD and the backport. There is one merge conflict in licensing.

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Depends on: https://git.openjdk.org/jdk11u-dev/pull/1603

Commit messages:
 - 8221621: Crash in KlassFactory::check_shared_class_file_load_hook
 - 8221621: FindTests.gmk cannot handle "=" in TEST.groups comments

Changes: https://git.openjdk.org/jdk11u-dev/pull/1604/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=1604&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8221351
  Stats: 119 lines in 12 files changed: 86 ins; 17 del; 16 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/1604.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev pull/1604/head:pull/1604

PR: https://git.openjdk.org/jdk11u-dev/pull/1604