[jdk21u-dev] RFR: 8318585: Rename CodeCache::UnloadingScope to UnlinkingScope

[Goetz Lindenmaier]

I backport this for parity with 21.0.4-oracle.

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Commit messages:
 - Backport 4eab39d9415b2ec5c2984d0d3c110e9364090835

Changes: https://git.openjdk.org/jdk21u-dev/pull/455/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=455&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8318585
  Stats: 14 lines in 7 files changed: 3 ins; 0 del; 11 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/455.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/455/head:pull/455

PR: https://git.openjdk.org/jdk21u-dev/pull/455