Updated SLEM build script for Kairos v2.4.3

[brathina-spectro]

This script incorporates the changes for Kairos framework v2.4.3 & also takes into consideration the feedback we got from SUSE Rancher about the base image we've built with Kairos components.

Feedback from SUSE:

We’ve had a look through the Dockerfile, along with the further details in the slides that you’ve shared with us, and we have a few concerns that I think are easily remedied:

1. We need you to build the image on a SLE Micro host, as what you’ve essentially done here is mixed SLES with SLE Micro from a package repo perspective, and whilst this will functionally work, it makes it much more challenging for us to support.
2. Following (1), we realise that when building on a SLE Micro host that you won’t have access to all the necessary packages, so we suggest that you pull the extra dependencies from OpenSUSE Leap 15.4 repos (http://download.opensuse.org/distribution/leap/15.4/repo/oss/ - these are binary compatible with SLES) – we’re happy to support the ~30 extra packages that are deployed from this repo.
3. You’re pulling in dhcp-client which pulls in several extra dependencies that may not be needed as DHCP is already taken care of by NetworkManager, which is installed by default… can we drop this requirement? I do note that your Kairos framework image creates a dracut requirement for the network-legacy
4. module (via /etc/dracut.conf.d/90-kairos-network-legacy.conf), but I’m wondering how essential this is to Kairos functioning if NetworkManager is available?
5. Can you explain why containerd is pulled in outside of k3s? Are you running additional containers on the host, outside of k3s? If so, are you pulling containerd from SLE repos, or is this something you’re providing and supporting yourselves?

[brathina-spectro]

@santhoshdaivajna could you review this PR? I'll cherry-pick this into the corresponding branch once this is merged