Restored production queue current item checks

Fixes regression #5948 where you could freely build any building by
canceling the production before deploying by restoring the currentItem
checks in the PlaceBuilding order to ensure that the production is still
valid.
Merge pull request #5955 from Squiggles211/production_cancel_fix

Restored PlaceBuilding order's ProductionQueue checks.
Merge the RA aircraft queues. Closes #5961.
Fix mouse event filtering in BackgroundWidget.
Allow ImageWidget to filter mouse events.
Fix mouseover filtering in cloned widgets.
Hide invalid hotkey from button tooltips.
Move TD production widgets into the RA project.
Don’t crash if there are no production icons. Fixes #5543.
Extract ProductionPalette background drawing into logic code.
Add support for single-line time display.
Extract sidebar logic into smaller classes.
Support fading the area behind the radar to black.
Blink the power display red when low power.
Add new RA UI.