[jdk21u-dev] RFR: 8321974: Crash in ciKlass::is_subtype_of because TypeAryPtr::_klass is not initialized

[Aleksey Shipilev]

Clean backport to fix C2 regression in JDK 21.

Additional testing:
 - [x] New regression test _passes_ even without a fix
 - [ ] linux-x86_64-server-fastdebug, `tier{1,2,3}`

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Commit messages:
 - Backport c8ad7b7f84ead3f850f034e1db6335bbbac41589

Changes: https://git.openjdk.org/jdk21u-dev/pull/119/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=119&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8321974
  Stats: 89 lines in 3 files changed: 54 ins; 22 del; 13 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/119.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/119/head:pull/119

PR: https://git.openjdk.org/jdk21u-dev/pull/119