Draft: add support for the PineNote!

This adds initial support for the PineNote, it includes a few hacks to make e-ink nicer:

• Overwriting the default Phosh theme with the postmarketos-paper theme
• Overwriting the postmarketos-splash config to use a black background

The splash config overwrite is a bit of a hack, it will be replaced once we move to the new WIP pbsplash and do the splash rendering at runtime, it's not a hack intended to remain for long.

I've also added two new deviceinfo variables:

deviceinfo_flash_rk_partition_kernel
deviceinfo_flash_rk_partition_system

This behave like deviceinfo_flash_fastboot_partition_kernel but for rkdeveloptool.

Please do build test this!

I've written up an install guide on the device wiki page, for right now you NEED UART to flash it as the BSP u-boot that ships with it is pretty crap, hopefully we can either replace this with a modified BSP u-boot to at least work around this until mainline u-boot support lands.

This depends on https://gitlab.com/postmarketOS/pmbootstrap/-/merge_requests/2165