[jdk11u-dev] RFR: 8277385: Zero: Enable CompactStrings support

[Aleksey Shipilev]

Clean backport to improve Zero performance.

Additional testing:
 - [x] Linux x86_64 Zero fastdebug `make bootcycle-images`

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Commit messages:
 - Backport 3f847fe89a088d6921107ca887a7a1bace871bd6

Changes: https://git.openjdk.java.net/jdk11u-dev/pull/726/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk11u-dev&pr=726&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8277385
  Stats: 2 lines in 1 file changed: 0 ins; 1 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk11u-dev/pull/726.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk11u-dev pull/726/head:pull/726

PR: https://git.openjdk.java.net/jdk11u-dev/pull/726