Reading properties from secrets in other namespaces

Hi!

Currently we create for each yaks test a secret, like shown in the [documentation](https://citrusframework.org/yaks/reference/html/index.html#configuration-secrets), were we store some of our credentials. Creating and maintaining the code and files however is quite cumbersome. It would be nice if one could label an already existing secret and read from it that is for example synced by an ExternalSecret. This sounds quite doable, but in our case the Secret will not be in the **same** namespace as the yaks test pod. Currently yaks is not able to read from a secret that is located in another namespace.

Read the configuration-secrets documentation linked in the issue and inspect how YAKS tests currently access secrets in their pod namespace. Determine how an existing, labeled Secret in another namespace should be selected and accessed, including the ExternalSecret use case; done means credentials can be read across namespaces without creating per-test secret files.

Written by the indexing model from the issue text.