Substitute BootLoader.loadClassOrNull(name) to fix a NPE with JDK 11

[gwenneg]

Fixes #6127

I'm submitting this as a draft to see if CI is happy with is (even if there's no reason it wouldn't). In the meantine, I'm just starting a full JDK 11 Quarkus native build locally to make sure the exception is gone for good and see if there's anything left to fix apart from the ConcurrentModificationException.

[gwenneg]

The GraalVM issue seems to be fixed, but I got two quarkus-integration-test-spring-data-jpa tests failures:

[ERROR] Failures: 
[ERROR]   PersonResourceTest.testJoinedAfter:178 1 expectation failed.
JSON path size() doesn't match.
Expected: is <0>
  Actual: 2

[ERROR]   PostResourceTest.testByPostedAtBefore:40 1 expectation failed.
JSON path size() doesn't match.
Expected: is <3>
  Actual: 0

[INFO] 
[ERROR] Tests run: 60, Failures: 2, Errors: 0, Skipped: 0

[geoand]

@gwenneg the PR seems to be OK now, did you just restart the tests?

[gwenneg]

The quarkus-integration-test-spring-data-jpa tests were successful after a second attempt. The failures were probably a consequence of my computer being super slow because of the full Quarkus native build.

[geoand]

OK cool, thanks for the info @gwenneg

[gwenneg]

I found one native build error unrelated to this PR, I'll check if there's already an issue opened about it and create a new one if not. This PR is ready to be reviewed and merged.

[geoand]

It looks perfectly reasonable to me but I haven't been following the latest GraalVM developments so I'll let others review and merge

[jaikiran]

On a slightly unrelated note, I think we will need a issue created to rollback/undo some of these Graal VM fixes within our Quarkus code, once these fixes come in directly from Graal VM 19.3.1 (or better still a CR of 19.3.1) release.

[gsmet]

@gwenneg can you open an issue with the list of the PRs that we will need to revert?

Thanks!

[gwenneg]

@gsmet Yes, I'll take care of it.

[gwenneg]

Issue created: #6179