Issue Description:

Simplify testing of the BuildItems produced by the drools-drl-quarkus extension, avoiding the need for a "fake" downstream extension just to test the content of the builditems.

ref https://github.com/quarkusio/quarkus/discussions/32389

Acceptance Criteria:

Using QuarkusUnitTest#addBuildChainCustomizer.

Out of Scope:

as not specified.

Additional Information:

see out of scope.