Gummiboot was dropped from Alpine. Switch to grub, which is what we use
for tablet-x86uefi too.
In contrary to tablet-x86uefi, run the grub-mkimage command directly
inside the device package:
* This avoids creating another confusing grub-x86 like package (looks
like the x86 version of alpine's grub package, as it's the case with
grub-efi-x86, but actually it is just the result of grub-mkimage).
* In contrary to grub-efi-x86, the resulting efi file is not shared
across several devices.
* It's consistent with uboot mkimage commands, which we also run in
device packages.
Related: 398b7aef0b
At the moment we have Contributor: lines on some packages (but not all of them),
but often they don't represent the actual contributors to the package very well.
E.g. when we added them retroactively to the device packages we only added
the initial contributor (which isn't necessarily the person
who made most of the work for a device...)
The Git history is the most representative source for figuring out
who contributed to a package, so there is no reason to duplicate that
into the APKBUILD.
[skip ci]: way too many packages
Prepare for better device categorization by moving everything to testing
subdir first.
[skip-ci]: chicken-egg problem: passing pmaports CI depends on pmbootstrap MR
depends on this MR
Related: postmarketos#16
