[foreign-memaccess+abi] RFR: Add tests

[Per Minborg]

This PR proposes adding some additional tests and also some cleanup of tests.

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Commit messages:
 - Bump copyright years
 - Add session tests
 - Add tests

Changes: https://git.openjdk.org/panama-foreign/pull/800/files
 Webrev: https://webrevs.openjdk.org/?repo=panama-foreign&pr=800&range=00
  Stats: 92 lines in 2 files changed: 62 ins; 0 del; 30 mod
  Patch: https://git.openjdk.org/panama-foreign/pull/800.diff
  Fetch: git fetch https://git.openjdk.org/panama-foreign pull/800/head:pull/800

PR: https://git.openjdk.org/panama-foreign/pull/800