[foreign-memaccess+abi] RFR: 8293510: Code style issues in the foreign API

[Per Minborg]

This PR fixes numerous code style issues. PRs like this are work intensive to review and contain subjective improvements which could be debated. I think it is better to make these changes now rather than later.

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Commit messages:
 - Fix import
 - Merge with foreign-memaccess+abi
 - Break out functionality into Utils
 - Reformat public interface declartions
 - Cleanup method parameters in internal classes
 - Cleanup method parameters in public classes
 - Rearrange code
 - Fix naming issue
 - Merge with foreign-memaccess+abi
 - Rename variable names
 - ... and 4 more: https://git.openjdk.org/panama-foreign/compare/fea1f25d...a7a12de8

Changes: https://git.openjdk.org/panama-foreign/pull/721/files
 Webrev: https://webrevs.openjdk.org/?repo=panama-foreign&pr=721&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8293510
  Stats: 7214 lines in 74 files changed: 3155 ins; 2982 del; 1077 mod
  Patch: https://git.openjdk.org/panama-foreign/pull/721.diff
  Fetch: git fetch https://git.openjdk.org/panama-foreign pull/721/head:pull/721

PR: https://git.openjdk.org/panama-foreign/pull/721