x/build: recent Linux kernel builder

[prattmic]

Most of our Linux builders run Container-optimized OS milestone 113, which runs a Linux 6.1 kernel.

Issues like #73141 only reproduce on newer kernels (6.11 in that case), so it would be nice to have builders much closer to the latest Linux release.

Stage one of this is probably to simply upgrade to a newer COS milestone, the newest of which would get us a 6.6 kernel.

I believe @mknyszek ran into issues with too many bits of randomness in ASLR for TSAN in newer kernels (or just a different kernel config in newer COS?). I believe that is worked around now.

Even better as a stage two would be to have a dedicated builder that is always on the latest stable kernel release. Unfortunately I'm not sure how we would automate such a builder. @dmitshur notes that this was the original intention of our Debian sid builder, but the new sid builder (#61112) is only using the sid container image on top of COS, so it still has the old kernel.

[dmitshur]

We can try moving the sid builder (#61112) to cos-dev (up from cos-113-lts). If that ends up being too new and too noisy to be useful, we can move down to something less bleeding edge like cos-beta or cos-117-lts. Sent you crrev.com/i/8198148.

CC @golang/release.