Support for DB tests with XA enabled

### Description

Databases should be tested with XA enabled when possible. This could be at least a smoke test that the DB connection works – probably in the new testsuite only.

This needs to run in GHA Actions with other Store IT tests.

### Discussion

_No response_

### Motivation

Avoid regressions like https://github.com/keycloak/keycloak/issues/39182

### Details

_No response_