[jdk21u-dev] RFR: 8330981: ZGC: Should not dedup strings in the finalizer graph

[Aleksey Shipilev]

Clean backport to fix a ZGC corner case.

Additional testing:
 - [ ] Linux x86_64 server fastdebug, `all` with `-XX:+UseZGC`
 - [ ] Linux x86_64 server fastdebug, `all` with `-XX:+UseZGC -XX:+ZGenerational`

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Commit messages:
 - Backport 2f2dc2289bce47d8071a86215218f345cce71dba

Changes: https://git.openjdk.org/jdk21u-dev/pull/917/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=917&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8330981
  Stats: 8 lines in 2 files changed: 4 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/917.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/917/head:pull/917

PR: https://git.openjdk.org/jdk21u-dev/pull/917