Standardize to chainloop.dev/v1 for apiVersion for policies

[jiparis]

We decided to standardize to chainloop.dev/v1 as API version for declarative resources. Currently, only contracts use it, but policies and policy groups still use the levacy workflowcontract.chainloop.dev/v1

Let's add support to new apiVersion in policy and policy groups, and also let's update documentation.

[migmartri]

note that it should be backward compatible