observe kernel config in package-linux repo

[fwilhe]

We need to be aware if our kernel config drifts apart too far from debian

for this, the general idea is

build kernel config with debian tooling from the salsa repo

do that for gl and for debian's config

diff the config

this should be a cli tool that can be run in package-linux, and potentially also in ci

we should have this for the current main branch (kernel 6.12)

this should allow us to view config drift in kernel patch updates, but also between major version bumps (6.12 to 6.18)

[SujanaSubr]

gardenlinux/package-linux#206