[CLK] Embed dist-git in source branch

[bmastbergen]

This is a first pass at embedding the CLK dist-git in kernel-src-tree. I've started with the 6.12.74 srpm contents and then tweaked them a bit in the subsequent commits:

• Remove kabi generation and checking
• Move netfilter modules to modules-core to match Rocky 9
• Use configs from ciq/configs instead of copies in SOURCES

And then I added a utility script to generate the source tarball for the srpm.

When we rebase, I have lt_rebase.sh updating the spec to match the kernel we are rebasing onto. See that PR here:
ctrliq/kernel-src-tree-tools#60

And an example of what a rebase on top of this looks like in this branch:
https://github.com/ctrliq/kernel-src-tree/tree/%7Bbmastbergen%7D_ciq-6.12.y-next

Some things I'd like input on:

• Should SOURCES and SPECS be in the root directory, or should I move them into the ciq directory?
• Should all of these SOURCES and SPECS commits start with [CIQ] ?
• I added generate_tarball.sh as a script here so that when we do secure boot builds, those folks can generate the tarball without having to check out any other code. Cool?
• The lt_rebase.sh spec update will create a commit every time we rebase. I think thats ok to start, but maybe in the future we'd want to auto squash these or something? We may want to do that with the config commits eventually as well. Not sure.
• Deiter had suggested having no SOURCES directory and no tarball at all, since this repo IS the sources. But I couldn't get that to work. My (and Claude's) spec-fu may be too weak for that.
• That being said I don't think we need to push a tarball to any kind of lookaside. If a person checks out the 'dist-git' they are getting all of the source. If they want the tarball, they can call generate_tarball.sh.
• These PRs do not provide any tooling for the scenario where we want to release additional commits without performing a rebase (ie 6.12.74-2). We will need a workflow and tooling for that, but I wanted to start with the basics here.
• I think there is a lot of other stuff we can clean out of the kernel.spec and SOURCES dir. But again, I wanted to start simple, with the least amount of change. These cleanups can be done later.

Once we get this nailed down for 6.12, I'd apply a similar set of commits to ciq-6.18.y as well.

[bmastbergen]

I think I'll need to pull in this new kernel-pkg change as well:
https://github.com/ctrliq/kernel-pkg/pull/14/

[bmastbergen]

Updated:

• Use zstd for source tarball
• Picked up @elguero changes for module signing