Fallback probing

[samcday]

SHIFT is graciously working on changes to the shift6mq bootloader to ensure it includes more identifiable info in the vars: https://codeberg.org/amartinz/android_bootable_bootloader_edk2/commit/3277b00a272f3d75eafe0a9ffbc902d22d860208. We don't yet have a way to handle this properly.

Probably the most sensible approach is to include some basic boolean support for probes, so that the shift-axolotl DevPro can be modelled like so:

probe:
  - or:
    -
      - fastboot.getvar: serialno
        starts_with: S6MQ
      - fastboot.getvar: product
        equals: sdm845
    -
      - fastboot.getvar: model
        starts_with: axolotl

I dunno if we'd need any other operator besides or... The top level list of probes is already implicitly AND.