RFR: 8369150: NMethodRelocationTest fails when JVMTI events not published before JVM exit [v3]

[Chad Rakoczy]

> [JDK-8369150](https://bugs.openjdk.org/browse/JDK-8369150)
> 
> The test checks for JVMTI `COMPILED_METHOD_LOAD` and `COMPILED_METHOD_UNLOAD` events to be published for a relocated nmethod. It would originally intermittently fail if the JVM exited before it had time to publish the events so now it loops and forces GCs to encourage event publishing. The test fails if the events are received in the incorrect order (such as an unload before a load) or if the correct events are not received and the test times out.

Chad Rakoczy has updated the pull request incrementally with one additional commit since the last revision:

  Move validation logic to agent

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/28683/files
  - new: https://git.openjdk.org/jdk/pull/28683/files/d1577f8e..cc926342

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=28683&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28683&range=01-02

  Stats: 137 lines in 2 files changed: 46 ins; 76 del; 15 mod
  Patch: https://git.openjdk.org/jdk/pull/28683.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28683/head:pull/28683

PR: https://git.openjdk.org/jdk/pull/28683