start making SPI configurable

[markusdd]

This is work in progress to make SPI pins configurable as the old hardcoded approach breaks down as described in #806

[markusdd]

This PR basically ready for review by you @lumapu .

It switches to the cutsom SPIClass constructor while keeping backward compatibility, which should be tested by people who own a classic ESP32 and ESP8266.
For ESP82 the web interface disables the new SPI pin selection as it is impossible on that chip.

Also, the available pinlist for esp32s3 has been added, as it has more pins and more flexibility even compared to the ESP32.
(otherwise e.g. pins 47/48 are inaccessible for config)

[lumapu]

looks really good to me, thank you for your contribution!
I will check the code on a ESP8266 before I will merge this PR into the next dev-build

[markusdd]

I should note that it is probably necessary to do a complete config erase for this build as it alters the configuration structure, I at least noticed some weird config display (actually it is logical as we expanded the pinout section, so the old config layout won't match)