APRS RX: better region/frequency controls

[gullradriel]

Fix for APRS-RX settings not retained ( https://github.com/portapack-mayhem/mayhem-firmware/issues/2339 )

• added MAN for manual
• added region and manual frequency as app settings
• added manual frequency input view (press middle button on frequency open the keypad)
• set default region to North America with default corresponding frequency (in case it was never set, which will be the case on first app launch or on portapacks without sdcards)