[WFCORE-6312] Add version 18 of the WildFly Elytron model and schema

[fjuma]

https://issues.redhat.com/browse/WFCORE-6312

Creating this as a draft PR for now since we have at least one RFE being worked on right now that needs this. This can be merged once we have an RFE that has been pre-checked.

[yersan]

CC @ehsavoie since he can help with the yaml failures

[fjuma]

@ehsavoie Would you be able to help with the yaml failures? I haven't been able to look closely yet but I'm not sure where it's getting the urn:wildfly:elytron:17.0 value from since it looks like I've updated that to urn:wildfly:elytron:18.0 in most places. Thanks!

[yersan]

@fjuma It looks like these XML files are the bad guys:

https://github.com/wildfly/wildfly-core/blob/main/testsuite/manualmode/src/test/resources/org/jboss/as/test/manualmode/management/persistence/testWithCli.xml#L90
https://github.com/wildfly/wildfly-core/blob/main/testsuite/manualmode/src/test/resources/org/jboss/as/test/manualmode/management/persistence/test.xml#L87

[ehsavoie]

@fjuma PR sent on your branch fjuma#4

[fjuma]

Thanks very much @yersan and @ehsavoie! I've just merged @ehsavoie's PR against my branch.

[darranl]

Please don't make any further changes to this PR - I am going to combine it with a couple of other PRs so we can get them merged together.

Thank you for this implementation.