Draft - Deferred connection evaluation

[LeonMatthesKDAB]

Having the ability to control when a connection is emitted could be advantageous, especially in a multi-threaded context, where a worker thread might emit a signal, but the slot should be called in an event loop on a GUI thread.

To control when exactly a connection is evaluated, implement a ConnectionEvaluator, similar to the BindingEvaluator, that can control when exactly a slot is called.

Add a function connectDeferred (or similar) that takes a ConnectionEvaluator as the first argument, then takes the same arguments as the normal connect function.
This slot would then queue the actual function to be called in the ConnectionEvaluator. The queued functions in the ConnectionEvaluator could then be called at any time, similar to how evaluateAll works on the BindingEvaluator.
The difference here would be that connections might actually be emitted multiple times between calls to the evaluator, so these calls would then also need to be emitted multiple times.

[LeonMatthesKDAB]

We added experimental support for this in #48 🥳