RFR: 8369734: JvmtiExport::post_class_file_load_hook return value is never used

[Francesco Andreuzzi]

`JvmtiExport::post_class_file_load_hook` returns a boolean, which tells whether the hook modified the class data or not. Users of the function write the same check on their own. I propose replacing the handwritten check with the boolean returned by `post_class_file_load_hook`.

Passes tier1 and tier2 (fastdebug).

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Commit messages:
 - use

Changes: https://git.openjdk.org/jdk/pull/27777/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27777&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8369734
  Stats: 15 lines in 1 file changed: 0 ins; 1 del; 14 mod
  Patch: https://git.openjdk.org/jdk/pull/27777.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27777/head:pull/27777

PR: https://git.openjdk.org/jdk/pull/27777