* Make ST7789 accept only full config with SPI pins
* Make Generic ST7789 wrapper library handle "slot"
* Update Round LCD and 240x240 Square LCD
* Remove Python Round LCD and 240x240 LCD modules (we need the space!)
* Remove C++ Round LCD and 240x240 LCD libraries (they're a little redundant!)
* Fix garbage collected framebuffer bug in Python ST7789
* Deprecate "flip" in favour of "configure_display"
* Tidy up ST7789, remove dead/unused/commented code
Removes all driver-specific SDA/SCL pin definitions and defaults.
Pin type is "uint" everywhere, but "PIN_UNUSED" is *int*_max for MicroPython compat. That's still a lot of pins!
Adds baudrate to the I2C class, and allows a driver (like Trackball) to check the baudrate is supported
* Add a common/pimoroni.hpp to list default pins for various add-ons
* Move the BG SPI Slot enum here for safe keeping
* Switch all GPIO pin references to "uint" to match Pico SDK and bring back PIN_UNUSED as UINT_MAX
Phil Howard