RFR: 8227060: Optimize safepoint cleanup subtask order

Fri Jul 15 12:45:39 UTC 2022

Most of the analysis in the PR is for code that's removed, but I found one safepoint cleanup task that's unused.  Also the dictionary resizing and symbol/string table rehashing, while rare, could take a long time so I moved them sooner in the list.
Tested with tier1-3.

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Commit messages:
 - 8227060: Optimize safepoint cleanup subtask order

Changes: https://git.openjdk.org/jdk/pull/9515/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9515&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8227060
  Stats: 37 lines in 5 files changed: 13 ins; 21 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/9515.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9515/head:pull/9515

PR: https://git.openjdk.org/jdk/pull/9515