RFR: 8341796: Fix ExceptionOccurred in jdk.hotspot.agent

[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.

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Commit messages:
 - init

Changes: https://git.openjdk.org/jdk/pull/21813/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21813&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8341796
  Stats: 26 lines in 5 files changed: 0 ins; 0 del; 26 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