RFR: 8290464: Optimize ResourceArea zapping

[Aleksey Shipilev]

See the rationale in the bug.

Additional testing:
 - [x] Linux x86_64 fastdebug, `FieldSetAccessibleTest` (~10% usr time improvement)
 - [ ] Linux x86_64 release, `FieldSetAccessibleTest` (no regressions)
 - [x] Linux x86_64 fastdebug, `hotspot:tier1` (~5% usr time improvement)
 - [ ] Linux x86_64 release, `hotspot:tier1` (no regressions)
 - [ ] Linux x86_64 fastdebug, `tier1` (???% usr time improvement)
 - [ ] Linux x86_64 release, `tier1` (no regressions)

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Commit messages:
 - Fix

Changes: https://git.openjdk.org/jdk/pull/9543/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9543&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8290464
  Stats: 28 lines in 1 file changed: 20 ins; 3 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/9543.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9543/head:pull/9543

PR: https://git.openjdk.org/jdk/pull/9543