RFR: 8378700: Migrate lang/annotation tests away from TestNG

Wed Feb 25 16:22:11 UTC 2026

Remove the use of TestNG from java/lang/annotation tests.
Interesting that JUnit scans annotations on member classes, so we can't put malformed annotations on classes nested in the test class; we can put them on package-private classes in the same source file instead.
Also refactored LoaderLeakTest to perform GC more reliably within our test framework.

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Commit messages:
 - Remove testng from annotation package

Changes: https://git.openjdk.org/jdk/pull/29921/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=29921&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8378700
  Stats: 309 lines in 7 files changed: 88 ins; 119 del; 102 mod
  Patch: https://git.openjdk.org/jdk/pull/29921.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29921/head:pull/29921

PR: https://git.openjdk.org/jdk/pull/29921