RFR: 8340988: Update jdk/jfr/event/gc/collection tests to accept "CodeCache GC Threshold" as valid GC reason

[Leonid Mesnik]

Tests
jdk/jdk/jfr/event/gc/collection/TestGCCauseWith* GC
check the GC reasons. They GC might be caused by
"CodeCache GC Threshold"
if test is executed with Xcomp and GC caused by codecache cleanup.

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Commit messages:
 - fix

Changes: https://git.openjdk.org/jdk/pull/21238/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21238&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8340988
  Stats: 10 lines in 4 files changed: 2 ins; 0 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/21238.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21238/head:pull/21238

PR: https://git.openjdk.org/jdk/pull/21238