feat: substitute disk commands by pure golang

[Itxaka]

Currently we require several binaries both on agent and immucore to exist in the system.

This brings packages that might not be needed after install or that are a commodity (mount can be called directly as a syscall for example)

We should have a look into substituting those by a pure golang implementation like https://github.com/diskfs/go-diskfs

That means:

• less dependencies in the underlying OS
• more interoperability between systems (especially libc vs musl)
• smaller images
• less points of failure (required binaries on the install image, on the initramfs, probable desync)

[Itxaka]

potentially we could also build the isos with it but Im not sure it would support all of our options like hybrid isos and such

EDIT: it actually does: https://github.com/diskfs/go-diskfs/blob/master/examples/bootable_iso.go#L44

[Itxaka]

part of this is already done with the new partitioner but deps have not been updated.

There is also the thing that yip still requires the binaries, which means the same partitioner changes should be try to move into yip so we can drop more deps from the os images. Currently we could drop binaries from the os image but immucore which uses yip still requires them so no luck there.