Pick SSID with strongest RSSI in mesh networks with multiple identical SSIDs

[mha1]

Home networks in mesh configuration can have multiple identical SSIDs (with different BSSIDs). Connecting an ELRS device to a home network should pick the BSSID with the strongest RSSI for the SSID to be connected.

The underlying Arduino library defaults to the scan method WIFI_FAST_SCAN which picks the first matching SSID for WiFi.begin(ssid,...). This can lead to WiFi.begin() randomly picking a device (e.g. router) which is further away than a close by other device (e.g. repeater) resulting in an unstable connection with connection losses. See also https://discord.com/channels/596350022191415318/1033101924494487582/threads/1197516934028218408

The fix is to change the default behavior for scanning network devices from the default WIFI_FAST_SCAN to WIFI_ALL_CHANNEL_SCAN which will take in account all devices on the network. In combination with sort method WIFI_CONNECT_AP_BY_SIGNAL (which is already default) the strongest BSSID for the given SSID will be connected.

https://github.com/espressif/arduino-esp32/blob/099b432d10fb4ca1529c52241bcadcb8a4386f17/libraries/WiFi/src/WiFiSTA.h#L74-L77

[pkendall64]

Nice one