[jdk21u-dev] RFR: 8317350: Move code cache purging out of CodeCache::UnloadingScope

[Goetz Lindenmaier]

I backport this for parity with 21.0.4-oracle.

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Commit messages:
 - Backport bd3bc2c6181668b5856732666dc251136b7fbb99

Changes: https://git.openjdk.org/jdk21u-dev/pull/433/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=433&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8317350
  Stats: 60 lines in 7 files changed: 26 ins; 6 del; 28 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/433.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/433/head:pull/433

PR: https://git.openjdk.org/jdk21u-dev/pull/433