Unify Movie Clips and Images loaded in the Sequencer with the rest of Blender's datablocks

If add a movie clip to the Sequencer, I feel as though should also be able to open that same clip in the Movie Clip editor. Currently, it is impossible to do so, and you have to load the clip into the Movie Clip editor separately. This feels redundant, and like a waste of memory to hold two of the same thing in the file.

Having this functionality could also create more parity with other video editors such as Premiere and Davinci that make use of a "Source" monitor that displays a clip before it is added to a timeline.