RFR: 8319560: Reformat method parameters in the FFM API

[Per Minborg]

This PR proposes to reformat some method parameters in the FFM API. The proposed changes are a bit opinion based eve though there are some underlying principles.

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Commit messages:
 - Harmonize method parameter layouts

Changes: https://git.openjdk.org/jdk/pull/16527/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16527&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8319560
  Stats: 28 lines in 4 files changed: 15 ins; 0 del; 13 mod
  Patch: https://git.openjdk.org/jdk/pull/16527.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16527/head:pull/16527

PR: https://git.openjdk.org/jdk/pull/16527