Allow mouse-wheel adjustment of settings controls

[louispires]

Summary

• adjust numeric spin settings with the mouse wheel while hovered
• cycle regular and editable combo-box settings, including Fill Density
• claim wheel input so scrollable settings panels do not move at the same time
• preserve normal scrolling while a combo-box popup is open
• ignore disabled controls and respect combo-box bounds

Testing

• built slic3r-shared-tests in Release mode
• passed focused mouse-wheel tests: 6 test cases, 16 assertions
• built slic3r-app-launcher in Release mode with 0 errors
• manually verified numeric fields, dropdowns, Fill Density, Favorites, and Full Settings on Windows

Build configuration used no-occt, SLIC3R_PCH=OFF, and SLIC3R_ENABLE_WIN10_MESH_REPAIR=OFF.

[louispires]

Quick preview of the functionality - Hover over the setting and then using my Mouse Wheel up and down

Allow.mouse-wheel.adjustment.of.settings.controls.15607.2.mp4