[jdk23u] RFR: 8337753: Target class of upcall stub may be unloaded

[Jorn Vernee]

Backport of: https://github.com/openjdk/jdk/pull/20479

There were some trivial conflicts in `stubGenerator_aarch64.cpp` and `stubGenerator_riscv.cpp`. Some code still there in jdk23, already removed in later versions.

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Commit messages:
 - Backport 8337753

Changes: https://git.openjdk.org/jdk23u/pull/163/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk23u&pr=163&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8337753
  Stats: 333 lines in 23 files changed: 255 ins; 26 del; 52 mod
  Patch: https://git.openjdk.org/jdk23u/pull/163.diff
  Fetch: git fetch https://git.openjdk.org/jdk23u.git pull/163/head:pull/163

PR: https://git.openjdk.org/jdk23u/pull/163