Add E2E gating tests to cover VES stndDefined domain, esp. when external schemas are used for validation.

Expected test-objects:

1. stndDefined events -> schema validation testing
2. stndDefined events -> stndDefinedNamespace routing
3. stndDefined events -> 2nd stage validation "optional" setting
4. stndDefined events -> 2nd stage validation (successful and expected failure scenarios).