Do not pass all editors to extensions

[isidorn]

Currently we have an issue that if an editor is registered in the modelService this editor will get passed to all the extensions via the api.
On the other hand if the editor is not registered in the modelService custom keybindings will not work and inteli-sene will not be supported.

We need a solution for an editor to not be passed to the extensions but still have custom keybdinings support and other editor goodnes.

Use cases: repl input, breakpoint widget, git commit input
Related: #10451

@alexandrudima could you provide some code pointers such that I can start looking into this.

@weinand fyi

[isidorn]

Fixed via f470ce1