Decouple framework-specific (ember/glint) stuff in @rehearsal/ember

[egorio]

Rehearsal is "naturally" becoming very tightly coupled with ember/glint framework.

It's better to decouple those stuff (glint plugins / migration-graph-ember / ServiceInjectionsTransformPlugin, etc.) using interfaces to framework-specific packages, like @rehearsal/ember... and use those functions as "extensions" for @rehearsalworkflow based on target package environment.