Compartmentalize `dataEditorClient.ts`

The `./src/dataEditor/dataEditorClient.ts` file has grown into a monolithic class and is beginning to render server / UI issues for the data editor. One example would be the recent #932 & #961 where the session & server disposals were not properly being disposed of.

This was because the `DataEditorClient` class was improperly registering its disposables. This would have been easily managed if the session, panel, and client/server portions of the class were their own components.

Also, with the addition of the data editor replacing the hex viewer ( #926 ) there will be a need for these components to behave differently if the data editor is being ran in a debug session or standalone.