Utilizing Label Selectors

[csviri]

Label selectors could be utilized for different purposes. But one reason is to do sharding for deployment of the operator, so by certain running instances, only selected Glue and GlueOperator resources would be selected.
To achieve this, we can add a label selector field in spec for both resources. GlueOperator would also propagate the label selector to Glue.

It is a question whether we should propagate labels and label selectors automatically for dependent resources. This would be a little problematic if there is a dependent resource and a related resource for the same type, in this case, we create only one informer, and label selectors don't support or.