Firewall: Groups: migrate to MVC

[fichtner]

Important notices

Before you add a new report, we ask you kindly to acknowledge the following:

• I have read the contributing guide lines at https://github.com/opnsense/core/blob/master/CONTRIBUTING.md
• I am convinced that my issue is new after having checked both open and closed issues at https://github.com/opnsense/core/issues?q=is%3Aissue

Is your feature request related to a problem? Please describe.

Static pages need to be removed eventually. Services page offers opportunity for it and enables API handling of the functionality.

Describe the solution you like

Simple inline migration/

Describe alternatives you considered

N/A

Additional context

N/A