Revert to nonos-sdk 2.2.1, new sdk-switching option in IDE menu for generic board only (#5763)

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

libraries/ESP8266WiFi/src/ESP8266WiFiSTA.cpp

@@ -138,7 +138,9 @@ wl_status_t ESP8266WiFiSTAClass::begin(const char* ssid, const char *passphrase,
     }
 
     conf.threshold.rssi = -127;
+#ifndef NONOSDK221
     conf.open_and_wep_mode_disable = !(_useInsecureWEP || *conf.password == 0);
+#endif
 
     if(bssid) {
         conf.bssid_set = 1;