RFR: 8333841: Add more logging into setfldw001 tests.

[Leonid Mesnik]

Tests
SetFieldAccessWatch/setfldw001
SetFieldModificationWatch/setfmodw001
intermittently fail with Xcomp. I was unable to reproduce the problem.
The fix adds more checks and variants with jvmti logging.

The goal is to understand why the test fails.
1. Confirm that the event is not sent. Currently, the test doesn't differ between sending "NULL" event and not sending an event at all. 
2. Check if the interpreter-only mode is switched too late in Thread-1. The jvmti logging shows when field events are enabled and when each thread actually switches to interpreter-only and enables event handling. 

The plan is to try to reproduce the failure and remove '@test id=logging'  after https://bugs.openjdk.org/browse/JDK-8205957 is fixed.

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Commit messages:
 - 8333841: Add more logging into setfldw001 tests.

Changes: https://git.openjdk.org/jdk/pull/19612/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19612&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8333841
  Stats: 35 lines in 5 files changed: 31 ins; 2 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/19612.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19612/head:pull/19612

PR: https://git.openjdk.org/jdk/pull/19612