RFR: 8345422: Fix JNI Checker "in native method" warnings in the debug agent and debugger tests

[Chris Plummer]

The root cause of [JDK-8344804](https://bugs.openjdk.org/browse/JDK-8344804) seems to be some JNI Checker warnings. I decided to resolve all the warnings in the debug agent and debugger tests that start with "in native method". This seems to have resolved [JDK-8344804](https://bugs.openjdk.org/browse/JDK-8344804) failure. There are still other JNI Checker warnings present that are not being dealt with at this time.

Testing in progress:
- [ ] All tier1
- [ ] All tier2 svc tests
- [ ] All tier3 svc tests
- [ ] All tier4, which is where [JDK-8344804](https://bugs.openjdk.org/browse/JDK-8344804) reproduced
- [ ] All tier5 svc tests

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Commit messages:
 - Fix some debugger related JNI Checker warnings.

Changes: https://git.openjdk.org/jdk/pull/22528/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22528&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8345422
  Stats: 108 lines in 9 files changed: 64 ins; 24 del; 20 mod
  Patch: https://git.openjdk.org/jdk/pull/22528.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22528/head:pull/22528

PR: https://git.openjdk.org/jdk/pull/22528