This commit allows switching SDK firmware:
nonos-sdk-pre-v3 shipped with release 2.5.0 has issues:
* Some boards show erratic behavior (radio connection is quickly lost), with an unknown cause.
These boards work well with previous nonos-sdk-2.2.1 firmware (#5736)
* Overall performances seem to have decreased (#5513)
This PR restores sdk2.2.1 (as in core-2.4.2).
SDK-pre-3.0 - which has brought long awaited fixes (WiFi sleep modes) - is still available through a menu option available only with generic board.
BREAKING
* new define `-DNONOSDK221=1` or `-DNONOSDK3V0=1`
* for external build systems: new library directory: `tools/sdk/lib/<version>/lib`
* PIO: variable `PIO_FRAMEWORK_ARDUINO_ESPRESSIF_SDK3` is needed for sdk-pre-v3.
Fix#5736
* dynamic WiFi.hostname("newname")
* WiFi.hostname() back to String return type
* no silent hostname fix but proceed with debug message and returning false
* fwupdate
* fw update to latest version:
WPA working, WEP+Open disabled by default. Need API change.
* helpers to follow sdk updates
* remove compare scripts - made a separate PR for them
* add wep api, restore original espressif comment (wep enabled does not prevent wpa)
* libmain was not up to date
* experimental: DTIM setting in WiFi.setSleepMode(WIFI_LIGHT/MODEM_SLEEP, DTIM-value)
with new getter: .getListenInterval() / .isSleepLevelMax()
* fixes
* fix debug message
* when not using listenInterval, set wifi sleep level to min
* update documentation
* update doc
* minimum changes for libraries to compile with lwip2
* add WiFiClient::availableForWrite() (similar to Serial::) which indicates how much data can be sent without buffering
In WPA protocol, the maximum length of the passphrases are 64 characters in order to distinguish them from the actual PSK who is 64 ASCII characters long, so in most systems if a 64 chars string is passed, it is assumed to be a PSK, otherwise is treated as a passphrase and is used to compute the PSK.
