[foreign-memaccess+abi] RFR: Modernize code [v3]

[Per Minborg]

> This PR proposes to modernize some parts of the code with constructs from newer Java versions.

Per Minborg has updated the pull request incrementally with two additional commits since the last revision:

 - Rename and reformat
 - Use allocation free constructs

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Changes:
  - all: https://git.openjdk.org/panama-foreign/pull/894/files
  - new: https://git.openjdk.org/panama-foreign/pull/894/files/9b7e1fa6..14d54487

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=panama-foreign&pr=894&range=02
 - incr: https://webrevs.openjdk.org/?repo=panama-foreign&pr=894&range=01-02

  Stats: 36 lines in 2 files changed: 18 ins; 0 del; 18 mod
  Patch: https://git.openjdk.org/panama-foreign/pull/894.diff
  Fetch: git fetch https://git.openjdk.org/panama-foreign.git pull/894/head:pull/894

PR: https://git.openjdk.org/panama-foreign/pull/894