Fixed styling/layout/searching and filter buttons in Create Unit Dialog

[HUSSAR-mtrela]

replaced some hardcoded pixel values with with existing variables added a few comments that explain existing variables and logic for creating UI elements fixed initializing search box with keybinding mapped to opening Create Unit Dialog fixed styling/layout of UI elements fixed text and tooltips in source filter toggles (see issue #5388) excluded quantum beacons from playable units filter

TODO fix issue #5388 with some custom mods

[MrRowey]

@HUSSAR-mtrela Whats the status on this to be ready ?

[BlackYps]

Closing due to inactivity. Feel free to reopen it if you pick it up again.