Add option on Init command to set namespaces scan for CloudState operator inject sidecar

[sleipnir]

Add the ability to tell which namespaces to consider when scanning CloudState operator for sidecar proxy injection.

Set the property in cloudstate HOCON kubernetes config map

Example:
cloudstate.operator.watch.namespaces = ["my-namespace-1", "my-namespace-2"]

See:
https://cloudstate.io/docs/user/deployment/installing.html#operator-configuration

[sleipnir]

Example of command usage:

cloudstate init --inject-only=my-namespace