[jdk17u-dev] RFR: 8267186: Add string deduplication support to ZGC

[Zhengyu Gu]

I would like to backport this string deduplication patch to jdk17u. jdk17u is latest TLS version and this enhancement really helps memory footprint of applications that deal with a lot of `String`s

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Commit messages:
 - Backport abebbe2335a6dc9b12e5f271bf32cdc54f80b660

Changes: https://git.openjdk.org/jdk17u-dev/pull/1259/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=1259&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8267186
  Stats: 255 lines in 11 files changed: 219 ins; 9 del; 27 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/1259.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/1259/head:pull/1259

PR: https://git.openjdk.org/jdk17u-dev/pull/1259