initializer: move cryptsetup image into initializer

[jmxnzo]

This PR introduces the two commits of #1132 again, which have been reverted due to the release problems in #1150 .
Until now, we used a specific cryptsetup image, containing a couple of filesystem and mount tools that facilitate the LUKS encryption.
This PR is a first step to include the dependencies of the cryptsetup image in the initializer, while still keeping the bash entry point for now to allow setting up the LUKS device by the initializer. Thus all existing references to the specific cryptsetup image are dropped as part of this PR.

As a follow up the mounting/set up of the encrypted volume done by the bash entrypoint will be moved to a subcommand of the initializer binary.

K3s-QEMU-TDX: https://github.com/edgelesssys/contrast/actions/runs/12748493847
K3s-QEMU-SNP: https://github.com/edgelesssys/contrast/actions/runs/12748490036
AKS-CLH-SNP: https://github.com/edgelesssys/contrast/actions/runs/12748475625

[burgerdev]

Release v1.3.0 is out, so I'd say let's get this reapplied.

The commit history would be a bit easier to understand if you reapplied the commits (i.e., revert the reverts) instead of just rebasing the old branch.