Refactor ButtonFacade into something more appropriate

[blaise17]

With the upgrade to typescript 4 we can no longer facade the button by overriding properties with accessors (for details see #232 ).
We should probably have a look at ButtonFacade and what uses it and see what would be a more appropriate solution (as #233 means it's no longer a facade).

[psi77]

I think it would make sense to have something that is owned by the speechbar and does what the speechbar needs it to do. Then maybe add a couple of factory methods to convert buttons (and anything else we need to) into this new thing