Generate test resources compatible configuration for R2DBC

[wetted]

fixes #1353

[sdelamo]

We probably need to only add the properties only if TestResource feature is not present:

https://github.com/micronaut-projects/micronaut-starter/blob/3.6.x/starter-core/src/main/java/io/micronaut/starter/feature/database/DatabaseDriverConfigurationFeature.java#L41-L45

Moreover, we will probably have to extend from EaseTestingFeature to add the TestResource feature if the users select r2dbc feature.

I don't think we need the validator. We should only add TestResource with a compatible database. The users don't apply TestResource feature themselves.

And we need a test which verifies the username and password and url properties are not present in the database.