Improve help in `radar` so that with smaller displays help doesn't get cut off

[wcampbell0x2a]

• Reduce the size of the sections to the required size of the text in that section instead of just percentages
• Have a way of telling the user that some help is being cut off.

[wcampbell0x2a]

See https://github.com/rsadsb/adsb_deku/issues/176#issuecomment-1225918002 for an example of the help begin cut off.