RFR: 8341794: Fix ExceptionOccurred in jdk.attach

[Justin Lu]

Please review this PR which is part of the bigger umbrella bug: https://bugs.openjdk.org/browse/JDK-8341542.

This fixes incorrect usage of `jthrowable ExceptionOccurred(JNIEnv *env)` within _jdk.attach_.
This corrects instances where the return value is being treated as a boolean. Such occurrences are replaced with `jboolean ExceptionCheck(JNIEnv *env)`.

JNI Docs - ExceptionCheck
> We introduce a convenience function to check for pending exceptions without creating a local reference to the exception object. ... Returns JNI_TRUE when there is a pending exception; otherwise, returns JNI_FALSE.

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Commit messages:
 - init

Changes: https://git.openjdk.org/jdk/pull/21459/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21459&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8341794
  Stats: 3 lines in 1 file changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/21459.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21459/head:pull/21459

PR: https://git.openjdk.org/jdk/pull/21459