Drop MCC hack for layouts

[FloEdelmann]

As suggested in #5280 (review), this PR removes the mobile country code hack that provides different layouts depending on the country the quest is located in. A similar change has been made for the fire hydrant quest in #4369.
Now, no more layouts-mccXXX folders are left 🎉

Still left to remove in a future PR:

• The traffic_sign_background color (used in vector drawables) is still localized for SE, FI and IS via values-mccXXX/colors.xml files.
• The vibrating_button_illustration drawable image (used in quest_traffic_lights_vibration layout) is still localized for GB and AU via drawable-mccXXX-YYYdpi folders.
• The MCC logic is still included in AbstractQuestForm.

I'm not sure how to approach the color and drawable localizations. @westnordost do you have a suggestion?

[westnordost]

Yeah, very nice!

[westnordost]

I'm not sure how to approach the color and drawable localizations. @westnordost do you have a suggestion?

The Drawables are a bit of a black box in code, i.e. I don't think it would be feasible (not sure if possible) to modify their properties (i.e. some color) at runtime.

So, the traffic_sign_background would need to be removed from these drawables and instead new drawables like background_maxspeed_sign_yellow.xml need to be created. Which drawables are used for the layout then needs to be set prammatically.

[matkoniecz]

Thanks! I remember how confused I was by this mechanism (and still not entirely sure how it worked)