[jdk21u-dev] RFR: 8317299: safepoint scalarization doesn't keep track of the depth of the JVM state

[Martin Doerr]

Backport of [JDK-8317299](https://bugs.openjdk.org/browse/JDK-8317299). Needs manual integration in callnode.cpp, callnode.hpp, macro.cpp and vector.cpp because of unrelated context differences. All hunks are integrated.
In addition, I had to insert `@enablePreview` into the test update because MemorySegment is a preview API and is disabled by default in JDK21. Please review!

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Commit messages:
 - Backport 6d911f68a3244c40a62ab2570dfec68b8d0ed5d8

Changes: https://git.openjdk.org/jdk21u-dev/pull/716/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=716&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8317299
  Stats: 23 lines in 5 files changed: 15 ins; 0 del; 8 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/716.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/716/head:pull/716

PR: https://git.openjdk.org/jdk21u-dev/pull/716