[Features] Specify namespaces which kubeblocks should watch/observe

[lkadalski]

What is the user interaction of your feature
Use-case is that when I deploy operator it only watches specific namespaces for Cluster resources.

Is your feature request related to a problem? Please describe.
Only specific and secured namespaces should be maintained/observed/watched by kubeblocks.

If this is a new feature, please describe the motivation and goals.
Many operators have this feature so it's kind of expectation to be here

Describe the solution you'd like
it should be a config where we can specify list of namespaces. With default to all namespaces (as now).
If someone tries to add Cluster definition to not watched, it should not be pick up by kubeblocks.

Describe alternatives you've considered
I have not found any