Implement finalizer's uninstall

[geaaru]

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

Often we need to do operations after that a package is uninstalled, I think to the cleanup of icons cache, the remove of the files generated in the finalize phase, etc.

Describe the solution you'd like Run the uninstall finalizer phase instead of being a no-op

Describe alternatives you've considered

A separate cleanup.yaml file

Additional context

[mudler]

We already have the uninstall keyword in the finalizer, but since we don't save those in the system database, it is a no-op as for now

[geaaru]

Fine, :+1: