[jdk21u-dev] RFR: 8334769: Shenandoah: Move CodeCache_lock close to its use in ShenandoahConcurrentNMethodIterator

[Aleksey Shipilev]

Clean backport to sync up code bases and make the future backports clean.

Additional testing:
 - [ ] Linux AArch64 server fastdebug, `hotspot_gc_shenandoah`

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Commit messages:
 - Backport 4ebb77120af5a4ccbfde63b24cb50e05a3161f16

Changes: https://git.openjdk.org/jdk21u-dev/pull/868/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=868&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8334769
  Stats: 13 lines in 3 files changed: 3 ins; 8 del; 2 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/868.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/868/head:pull/868

PR: https://git.openjdk.org/jdk21u-dev/pull/868