[foreign-memaccess+abi] RFR: Rename and fix issues around CABI [v2]

[Per Minborg]

> I suggest renaming some variables to conform to naming conventions.
> This PR also contains other minor fixes.

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

  Rename two enum constants

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Changes:
  - all: https://git.openjdk.org/panama-foreign/pull/703/files
  - new: https://git.openjdk.org/panama-foreign/pull/703/files/5cee6591..64255d79

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=panama-foreign&pr=703&range=01
 - incr: https://webrevs.openjdk.org/?repo=panama-foreign&pr=703&range=00-01

  Stats: 14 lines in 3 files changed: 0 ins; 0 del; 14 mod
  Patch: https://git.openjdk.org/panama-foreign/pull/703.diff
  Fetch: git fetch https://git.openjdk.org/panama-foreign pull/703/head:pull/703

PR: https://git.openjdk.org/panama-foreign/pull/703