Inconsistent usage of ActionDispatcher

[tortmayr]

In GLSP we use an extended version of sprotty's ActionDispatcher that adds some additional API methods.
These API methods are not reflected in the default IActionDispatcher interface. As a consequence we often use the implementation type (GLSPActionDispatcher) directly when injecting. In the end we end up with different variants of injecting the action dispatcher:

// When we only use API methods from the default sprotty dispacher we often use:
@inject(TYPES.IActionDispatcher) protected actionDispatcher: IActionDispatcher

// When we need the extended API we either use
@inject(TYPES.IActionDispatcher protected actionDispatcher: GLSPActionDispatcher
// or 
@inject(GLSPActionDispatcher) protected actionDispatcher: GLSPActionDispatcher

In the end this is quite confusing and we end up with a weird mix of injecting either the implementation class directly, or injection the generic TYPE identifier and then set the type itself to the implementation class. In any case we have the implicit assumption here that the TYPES.IActionDispatcher class is always an instance of GLSPActionDispatcher.

While this assumption is very reasonable we should make it explicit. With @eclipse-glsp/sprotty package we have the possibility to directly add the additional API to the IActionDispatcher interface and can then consistently use the IActionDispatcher type for injecting.
In addition, this should also avoid potential breakages if an adopter binds a custom IActionDispatcher that is not derived from the GLSPActionDispatcher.