[foreign-memaccess+abi] RFR: 8292078: Thread-safety issues in AbstractLinker implementations [v3]

[Per Minborg]

> Change to lazy static initializing for singletons and fix a bug in `LinuxAArch64VaList` that threw an `IndexOutOfBoundsException`.

Per Minborg has updated the pull request incrementally with one additional commit since the last revision:

  Undo more reformatting

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Changes:
  - all: https://git.openjdk.org/panama-foreign/pull/702/files
  - new: https://git.openjdk.org/panama-foreign/pull/702/files/02d4dcd0..37558149

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=panama-foreign&pr=702&range=02
 - incr: https://webrevs.openjdk.org/?repo=panama-foreign&pr=702&range=01-02

  Stats: 13 lines in 1 file changed: 0 ins; 1 del; 12 mod
  Patch: https://git.openjdk.org/panama-foreign/pull/702.diff
  Fetch: git fetch https://git.openjdk.org/panama-foreign pull/702/head:pull/702

PR: https://git.openjdk.org/panama-foreign/pull/702