Today if a user builds firmware with an incorrect WiFi SSID or password,
they get a generic `WiFi disconnected.` error message.
Extend logging to descirbe the reason that WiFi was disconnected.
I gathered the updated logs for the 3 scenarios below.
```
WiFi: Attempting manual WiFi reconnect...
WiFi: WiFi disconnected (reason=ASSOC_LEAVE). Flagging for reconnect...
WiFi: WiFi disconnected (reason=4WAY_HANDSHAKE_TIMEOUT). Flagging for reconnect...
WiFi: WiFi disconnected (reason=4WAY_HANDSHAKE_TIMEOUT). Flagging for reconnect...
WiFi: WiFi disconnected (reason=4WAY_HANDSHAKE_TIMEOUT). Flagging for reconnect...
```
```
WiFi: WiFi disconnected (reason=NO_AP_FOUND). Flagging for reconnect...
```
```
WiFi: WiFi connected successfully!
WiFi: Got connection
```
Payloads of 166 or 167 bytes previously passed the frame-sized bound
(MAX_CHANNEL_DATA_LENGTH = 167) but were rejected by sendGroupData
against MAX_GROUP_DATA_LENGTH (165), causing ERR_CODE_TABLE_FULL (retry
later) to be returned instead of ERR_CODE_ILLEGAL_ARG.
Fixes#3345
- scope the serial config CLI to RP2040; it was exposing the rescue CLI
(cat/rm/erase) on every ESP32 WiFi build, which gates it behind a
physical long-press
- bound and space out RP2040 rejoins: the core's join busy-waits, so cap
it at 5s and retry every 30s instead of every 10s
- stamp the reconnect timer in setup(), so the first loop() doesn't tear
down an association that is still finishing DHCP
- treat stored credentials as a pair, and pass NULL (not "") for an open
network
- teach build_as_lib.py where SerialWifiInterface moved
arduino-pico's WiFi.begin() blocks for up to 2x its 15s timeout, which
stalled the mesh loop on every reconnect attempt; use beginNoBlock().
Log the IP when the link comes up, and the status code when retrying.
Store ssid/pwd in NodePrefs and set them with 'set wifi.ssid' /
'set wifi.pwd' over USB serial; build-time WIFI_SSID/WIFI_PWD stay as
the fallback. Headless WiFi builds get the config CLI on Serial, which
is otherwise unused there.
SerialWifiInterface has no ESP32-specific code, so move it to
helpers/wifi and reuse it on RP2040. Guard the ESP32-only WiFi
event/auto-reconnect calls and poll link state on RP2040 instead.
Huw Duddy