Enable Apparmor Confinement

[om26er]

This adds snapd strict confinement for Linux 5.4, it includes

• linux-yocto
• linux-raspberrypi

Patches are stolen from https://forum.snapcraft.io/t/apparmor-kernel-patches-for-5-x-kernels/19955/3

Also deletes unused patches and updates snapd to 2.51.5

[om26er]

I think we should change the snappy.cfg to make SQUASHFS support statically into the kernel instead of loading it as a module.

Reason: If a yocto system wants to boot from SquashFS (CONFIG_SQUASHFS=y), that will break the snapd build because kernel-module-squashfs won't be found

[asimfarooq5]

Is there an update to this, it would be really great to have confinement working

[om26er]

ping @bboozzoo, did you get a chance to look at this PR ?

Ultimately I would like to help maintain this project. We have a bunch of other improvements that we'd like to contribute to this project.

[om26er]

ping @bboozzoo

[bboozzoo]

The repo has moved to https://github.com/snapcore/meta-snapd. Please file an issue there.