Bring back M1/M2 key overlay values

[unststable]

The current button mapping mode (B1 and B2 are unified for keyboard and mouse and B3 as smoke) makes the 4th button useless, but at the same time there are a huge number of skins in which keyboard and mouse buttons have their skinned icons on the overlay itself and it contains the 4th button placeholder in sprite:

This is a bit inconvenient for skinning.

[12beesinatrenchcoat]

There's also another discussion open for this: #13043