feat(atp): build directly from atp source (2/2)

[AtomHare]

This Draft/PR adds support to build atp and export it as a docker layer image. So it can be easily layered on bazzite-dx images.
It uses directly the install process recommended by ATP, so it means less issues in case of an update.

It needs to be discussed but some config files can probably be removed from this repo unless it's wanted to override some default settings for atp.

it may be wanted to remove the default wayland sessions like kinoite7 is doing. => implemented

[bominic27644]

This seems like a better approach since it uses the upstream install script. This means that build scripts would not need updating for every change in the upstream repo.

[ledif]

It looks like the workflow is failing because of cosign. Try cherry-picking this commit that avoids signing for PRs: 211db0c.

[AtomHare]

I will split this PR in 2 parts. The first one will only contain everything required to build the apt-common layer.
The other one (this one) will contain the rest. That way it will be easier to test if the build works without using workarounds.