Removing the dependence of the manifest package on the distro package to
import manifest into distro.
Wherever arch names are needed, we use the enums from the platform
package instead.
This platform copies more files into `/boot` which are necessary to be
able to boot IoT on some single board computers.
We also immediately set this on the `Aarch64_IoT` platform which needs
u-boot to be placed in the `/boot`.
This closes#3312.
GCE requires an archive with specific (tar) options, so we should have a
platform format defined separately for it.
Add the GCE image types to the x86_64 arch using the new platform
format.
These objects describes the hardware an image runs on. Including
- architecture
- bootloader
- required firmware
Use the platform abstraction to move firmware packages out of the package set
definitions.
