Move XML/XSD validation test case to dist module

The StandardConfigsXMLValidationUnitTestCase and XSDValidationUnitTestCase tests validates that the XML and XSD files that are shipped with WildFly are valid.

However, these tests are run by the smoke test suite and it is possible that previous tests have modified the configuration file that is used by the running WildFly server for the tests.

This is mostly harmless (as these tests should cleaned up any modification when they are teared down) except when WildFly core is changing its schemas and the WildFly integration CI job is checking that WildFly core snapshots behave correctly.
At this point, the WildFly XML configuration files references the latest XML version that is released with Core but the core snapshots introduced more recent versions.

The tests uses the special property jboss.test.xml.validation.future.schemas to ignore the latest schema when using core snapshots.
Unfortunately, the previous smoke tests may have modified the configuration file that will be written with the latest core schema version.

To fix this issue, these 2 tests should be moved to the dist maven module so that they validate the actual configuration files shipped with WildFly before any test has an opportunity to modify them.