[jdk17u-dev] RFR: 8305425: Thread.isAlive0 doesn't need to call into the VM [v2]

[Aleksey Shipilev]

> Unclean backport to improve `Thread.isAlive` performance, and provide grounds for more backports in the area.
> 
> The majority of conflicts are due to integration of Loom in JDK 19, which reshaped some Thread code. I tried to change as little in 17u as possible to avoid the change fan-out.
> 
> Additional testing:
>  - [x] Linux x86_64 fastdebug `tier1 tier2 tier3`
>  - [x] Linux AArch64 fastdebug `tier1 tier2 tier3`

Aleksey Shipilev has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains five additional commits since the last revision:

 - Remove one line more
 - Merge branch 'master' into JDK-8305425-thread-is-alive
 - Adjust comment: drop the mention of non-existent FieldHolder
 - Touchups to minimize the difference
 - Backport 35cb303a2c0c8b32de257c02e012a1928a6b4594

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

Changes:
  - all: https://git.openjdk.org/jdk17u-dev/pull/1425/files
  - new: https://git.openjdk.org/jdk17u-dev/pull/1425/files/bf0d60c9..c5c32813

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=1425&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=1425&range=00-01

  Stats: 11750 lines in 1228 files changed: 6608 ins; 1111 del; 4031 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/1425.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/1425/head:pull/1425

PR: https://git.openjdk.org/jdk17u-dev/pull/1425