Add support for ILI948x displays (ILI9486 / ILI9488)

[mnishiguchi]

This PR adds an AtomVM/ESP32 SPI display driver for the ILI948x family (ILI9486 and ILI9488), based on what I ended up with after tinkering with atomgl.

Background

I built and tested this on an ESP32-S3 custom PCB (Piyopiyo PCB):

• https://github.com/piyopiyoex/piyopiyo-pcb

It was validated using:

• https://github.com/piyopiyoex/hello_atomvm_scene (via atomvm_scene)

This work also builds on earlier experiments from a Nerves-based LCD project where we tried a few different 3.5" LCD modules:

• https://github.com/piyopiyoex/hello_nerves_lcd_spi

What’s included

• New ILI948x SPI display driver implementation for AtomVM/ESP32
• Support for both:
  • ILI9486 (RGB565 / 16-bit)
  • ILI9488 (RGB666 over SPI / 18-bit, sent as 3 bytes per pixel)
• Basic runtime options:
  • compatible: ilitek,ili9486 or ilitek,ili9488
  • rotation
  • color_order: rgb / bgr (default: bgr)
  • enable_tft_invon (optional)

Notes

I don’t have deep experience with ESP32 display driver internals, so I would appreciate a careful review of the SPI/DMA usage and any AtomVM conventions I should follow more closely. Functionally, it has been stable on my hardware and test project so far.

Thanks for taking a look.

[bettio]

Thanks for opening this PR. It looks good.
On the long term maybe we might think about handling rgb666 colors without converting them to rgb565, but anyway it is good for merge as soon as the REUSE issue is fixed.