RFR: 8319955: Improve dependencies removal during class unloading

[Thomas Schatzl]

Hi all,

  please review this performance improvement to dependency removal during class unloading: instead of moving the dependencies item by item via a `cmpxchg`, batch this operation.

This makes that part of class unloading ~7x faster in my measurements (class unloading stress test, loading/unloading 6k classes).

Testing: tier1-7

Thanks,
  Thomas

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Commit messages:
 - fix compilation
 - Remove timing code
 - Cleanup
 - initial version, with logging code

Changes: https://git.openjdk.org/jdk/pull/16639/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16639&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8319955
  Stats: 42 lines in 2 files changed: 38 ins; 2 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/16639.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16639/head:pull/16639

PR: https://git.openjdk.org/jdk/pull/16639