[jdk25u-dev] RFR: 8371368: SIGSEGV in JfrVframeStream::next_vframe() on arm64

[Aleksey Shipilev]

Fixes up JFR CPU profiling regression in JDK 25. I can reproduce the failure with `jdk_jfr` tests on Graviton 3 machine.

This PR contains two changesets, because putting only one of them breaks platforms. The resulting commit is clean and tidy.

Additional testing:
 - [x] Linux AArch64 server fastdebug, `jdk_jfr`, 100x with `-XX:+PreserveFramePointer`
 - [x] Linux AArch64 server fastdebug, `jdk_jfr`, 100x

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Commit messages:
 - Backport 141aebca38bc683cbff8a2dfe0cb98d3f0186a8c
 - Backport 42f333352408e03389fb37ea8ad8537a4a271b6a

Changes: https://git.openjdk.org/jdk25u-dev/pull/88/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk25u-dev&pr=88&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8371368
  Stats: 3 lines in 2 files changed: 2 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk25u-dev/pull/88.diff
  Fetch: git fetch https://git.openjdk.org/jdk25u-dev.git pull/88/head:pull/88

PR: https://git.openjdk.org/jdk25u-dev/pull/88