Introduce support for the LilyGo T-Connect Pro (16MB flash, 8MB PSRAM).
Adds board definition (boards/t-connect-pro.json), PlatformIO environments (variants/lilygo_tconnect_pro/platformio.ini) and variant-specific target glue (variants/lilygo_tconnect_pro/target.{h,cpp}).
Includes a new ST7796 LCD display driver ( based on the existing and already included Adafruit SS7796S driver in SS77xx )