Move the ActiveGate structs to separate package

[0sewa0]

K8S-11245

Description

ActiveGate and related structs have been moved to their own package, as a first step (and proof of concept) to make the api packages more organized.

Look at commits for more details:

1. Extract common structs to common package
2. Remove dead code
3. Update CRD generation
4. Move the ActiveGate structs to separate package

Still TODO: Add tests for pkg/api/v1beta3/dynakube/activegate/props.go

How can this be tested?

No change in actual behaviour, mainly look at the changes in the usage of the activegate package and common package, ask questions if something is hard to understand.