DATAJPA-631 - ResourceLoader improvements in ClasspathScanningPersistenceUnitPostProcessor.

A custom ResourceLoader configured on ClasspathScanningPersistenceUnitPostProcessor is now propagated to the ClassPathScanningCandidateComponentProvider used for looking up entity classes. We also forward the configured environment so that profile annotations are evaluated as well.

Related issue: DATACMNS-591.
DATAJPA-632 - Fix SimpleJpaQueryUnit test after cleanups in Spring Data Commons.

We now use a JpaQueryMethod instance rather than a mock as isPageQuery() cannot be mocked anymore as it has been made final.

Related issue: DATACMNS-601.
DATAJPA-601 - Improve performance with Propagation.SUPPORTS for readOnly operation.

Prepare issue branch.
DATAJPA-601 - Improve performance with Propagation.SUPPORTS for readOnly operation.

Changed default propagation for read-only operations from REQUIRED to SUPPORTS.
This avoids creating unnecessary transaction synchronisations.

This change uses a different code path in org.springframework.transaction.support.AbstractPlatformTransactionManager.getTransaction(TransactionDefinition) than before. We now hit the case: "// Create "empty" transaction" in which avoids the creation of a new tx.


I verified this with an external example app.