Add APFPV mode switching

[henkwiedig]

This PR will add APFPV mode switching for SBC 2 beta 2 and greg's APFPV image.
Please remove/uncomment these lines in stream.sh:

# sudo systemctl is-active --quiet wifibroadcast || sudo systemctl restart wifibroadcast
# sudo systemctl is-active --quiet wifibroadcast@gs || sudo systemctl restart wifibroadcast@gs

apfpv-demo.mp4

[Lupinixx]

Build locally and tested it on my Runcam VRX. Works as expected, switched between APFPV and wfb-ng from the menu, did a flight with both.

[zhouruixi]

1. Should we store APFPV settings in the pp_rk configuration file instead of retrieving them from other software configurations via commands?

2. Would it be simpler and more flexible to use wpa_supplicant instead of networkmanager to manage connections?