RFR: 8272609: Add string deduplication support to SerialGC [v8]

[Denghui Dong]

> Hi team,
> 
> Please help review this change to add string deduplication support to SerialGC.
> 
> Thanks,
> Denghui

Denghui Dong has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:

  tidy

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5153/files
  - new: https://git.openjdk.java.net/jdk/pull/5153/files/9b6a1486..86da5446

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5153&range=07
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5153&range=06-07

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5153.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5153/head:pull/5153

PR: https://git.openjdk.java.net/jdk/pull/5153