RFR: 8341796: Fix ExceptionOccurred in jdk.hotspot.agent [v2]

[Justin Lu]

> Please review this PR which is a JNI cleanup to replace incorrect usages of `jthrowable ExceptionOccurred(JNIEnv *env)` with `jboolean ExceptionCheck(JNIEnv *env)` in _jdk.hotspot.agent_.
> 
> This is part of the bigger umbrella issue: https://bugs.openjdk.org/browse/JDK-8341542. This change only modifies instances where the exception object is not needed, and the method return value is being treated as if it were a boolean.

Justin Lu has updated the pull request incrementally with one additional commit since the last revision:

  for consistency, include the comments as well

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Changes:
  - all: https://git.openjdk.org/jdk/pull/21813/files
  - new: https://git.openjdk.org/jdk/pull/21813/files/f6cd840f..63e67af7

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=21813&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=21813&range=00-01

  Stats: 3 lines in 2 files changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/21813.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21813/head:pull/21813

PR: https://git.openjdk.org/jdk/pull/21813