GdkWin32: Rework scroll input handling

Accumulate fractional deltas and generate discrete scroll events only when a full detent is reached. EDIT: just remove generation of emulated discrete scroll events as those have to be removed altogether in GTK4

Bring back generation of smooth scroll events as the issues mentioned in #3581 (closed) do not seem to occur anymore.

Edited by Luca Bacci

Merge request reports