- `DisplayDevice` improvements related `DisplayDriver`
- Replaced incorrect usage of `spiBusHandle` with `spiHostDevice` in all SPI display devices
- Disabled `DisplayDriver` support for RGB displays for now
- Updated `GraphicsDemo` project for the above changes
- TactilityC improvements:
- created `tt_hal_device_find()`
- created `tt_hal_display_*`
- created `tt_hal_touch_*`
- created `tt_lvgl_*`
- export `tt_app_*` calls
