RFR: 8307806: Rename Atomic::fetch_and_add and friends

[Kim Barrett]

Please review this renaming of Atomic::fetch_and_add and friends to be
consistent with the naming convention recently chosen for atomic bitops.  That
is, make the following name changes for class Atomic and it's implementation:

- fetch_and_add => fetch_then_add
- add_and_fetch => add_then_fetch

Testing:
mach5 tier1-3
GHA testing

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Commit messages:
 - rename in tests
 - rename uses
 - rename impl

Changes: https://git.openjdk.org/jdk/pull/13896/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13896&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8307806
  Stats: 156 lines in 39 files changed: 0 ins; 0 del; 156 mod
  Patch: https://git.openjdk.org/jdk/pull/13896.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13896/head:pull/13896

PR: https://git.openjdk.org/jdk/pull/13896