RFR: 8307533: Use atomic bitset functions for metadata flags

[Coleen Phillimore]

Replace the bit set copies from metadata to use the Atomic functions.
Tested with tier1-4.

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Commit messages:
 - 8307533: Use atomic bitset functions for metadata flags

Changes: https://git.openjdk.org/jdk/pull/13843/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13843&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8307533
  Stats: 66 lines in 5 files changed: 4 ins; 55 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/13843.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13843/head:pull/13843

PR: https://git.openjdk.org/jdk/pull/13843