Add more automated tests for the Window class and all input methods

[xoofx]

The Window class is not super tested today, only two tests were developed for a basic coverage of the core internals.

The associated input device methods (Mouse, Keyboard, Cursor...) are also not automated and tested at all, only tested manually during development.

Not sure about the approach, specially to make it working on GitHub action. An option could be to send windows message directly to simulate user interaction but not sure how much this is practical...