classloader leak seemingly caused by `ClassValue` caching in `Util.findSam()`

[Ladicek]

Issue description

In #477, we got rid of ClassValue caching in Util.findSam(), which apparently caused a classloader leak. It feels like the classloader leak is elsewhere, or more subtle than that, but after spending two days staring into heap dumps and figuring out nothing, I'm just filing this issue for future reference.

CC @dmlloyd

[Ladicek]

Oh, reproduction steps:

1. Reinstate ClassValue caching and mvn clean install in Gizmo.
2. Change the Gizmo version string in Quarkus (at least in bom/application/pom.xml, but ideally in all places) to the just-built SNAPSHOT version.
3. Build the full Quarkus (-Dquickly etc.) from this PR: Qute: gizmo2 rewrite quarkus#49397 (or from my branch: https://github.com/Ladicek/quarkus/commits/arc-gizmo2/)
4. cd integration-tests/devmode and mvn clean verify -Dno-build-cache

To obtain a heap dump, one can add -XX:+HeapDumpOnOutOfMemoryError into the <argLine> value of the Maven Surefire plugin configuration in build-parent/pom.xml in Quarkus.

[dmlloyd]

#477 is the right fix. Thanks!