pmb.install: switch to GPT and implement the Discoverable Partitions Specification

This MR switches the default partition table scheme from MBR to GPT. It also adds the correct type UUIDs for each pmOS partition, ignoring Chromebook partitioning as we cannot touch those without a few workarounds.

Devices that require MBR will have to declare that in their deviceinfo so new installs don't break.

fixes https://gitlab.com/postmarketOS/pmaports/-/issues/3205