[lworld] RFR: 8341761: Update JNI methods to support new field and array layouts

[Frederic Parain]

Update JNI methods to support new field and array layouts.
Extend testing of JNI methods

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Commit messages:
 - Update JNI methods to support new layouts

Changes: https://git.openjdk.org/valhalla/pull/1427/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1427&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8341761
  Stats: 362 lines in 3 files changed: 340 ins; 14 del; 8 mod
  Patch: https://git.openjdk.org/valhalla/pull/1427.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1427/head:pull/1427

PR: https://git.openjdk.org/valhalla/pull/1427