It lets us move the variables in cmdline.txt to
deviceinfo_kernel_cmdline. We can thereafter drop the cmdline.txt file
entirely.
By setting deviceinfo_generate_cmdline_txt we tell boot-deploy to
generate /boot/cmdline.txt from deviceinfo_kernel_cmdline. boot-deploy
can then also add information about partition UUIDs to the cmdline,
which helps postmarketos-initramfs find the correct partitions.
Part-of: https://gitlab.postmarketos.org/postmarketos/pmaports/-/merge_requests/6630
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
Sandelinos