By reimplementing Datasource inactive/active handling and eager startup
through Arc's native features, which is better integrated and gives us
this behavior.

So that we correctly detect empty URLs.

Because it duplicates:

* ConfigUrlMissingDefaultDatasourceStaticInjectionTest
* ConfigUrlMissingDefaultDatasourceDynamicInjectionTest
* ConfigUrlMissingNamedDatasourceStaticInjectionTest
* ConfigUrlMissingNamedDatasourceDynamicInjectionTest

… datasources

Consequently:

* Skip the health check for datasources without a URL
* Fail on startup if datasources without URL are (statically)
  injected into user bean
* Fail on first access if datasources without URL are retrieved
  dynamically through CDI

…jected into user beans

By reimplementing Flyway's/Liquibase's inactive/active handling and eager
startup through Arc's native features, which is better integrated and gives
us this behavior.

For consistency with datasource documentation.