Store the last used BSSID and channel in the RTC and use it for initial WiFi connect attempt.
This does speed up the WiFI connection to about 1.8 sec after boot.
Old situation was connected at about 3.9 sec after boot.
When booting from cold boot, the strongest known RSSI is chosen first.
MQTT controller queue handling is now more aggressive in trying to get rid of buffered packets.
It also now accepts the MQTT messages before it is connected to WiFi (or when not yet reconnected)
See #2650
The counter wifi_connect_attempt is being used to determine whether the fallback SSID should be tried.
It is also used to determine whether a "quick reconnect" is possible using the BSSID and channel of the last successful connection.
If the connection is unstable, (last connection was active for over 5 minutes) then the connect attempt counter can be reset.
Move WiFi/Network related functions into separate files to keep them organized and easier to locate.
Also added lots of comments and some documentation on the state machine handling WiFi connect and reconnects.
Gijs Noorlander