[WIP] Add wifi manager for provisioning

[facchinm]

Implementation still incomplete (missing channel selection and a sane name for the automatic AP) + the landing page should be skinned

[sandeepmistry]

@facchinm it seems IDF v3.3 includes provisioning support: https://github.com/espressif/esp-idf/releases/tag/v3.3

New Wi-Fi Provisioning Manager

@ubidefeo thanks for linking in arduino-libraries/WiFiNINA#26 (comment)

[facchinm]

While extremely nice and integrated I don't think that using idf provision module is what we need.
1 - it's api based (doesn't expose a graphical webserver)
2 - only checks if the credentials are saved, not if the wifi network is reachable (this will require additional logic on our side)

It's only HUGE pro is BLE provisioning but of course it needs some kind of companion app.

[JAndrassy]

some inspiration from the WiFiLink firmware?
default hostname was the board's name
and the skin made by arduino.org has the right color I think :-)