CI: Add Debian 12 (bookworm) jobs
This series adds another set of jobs, building on both Debian bullseye (the current version we build on) as the LTS distribution version, and Debian bookworm (the current version, just released).
Most of this is quite intensely boring, but it did involve upgrading virtme (for qemu command-line changes), Mesa (upgrade required to build against newer LLVM), and the kernel (no compelling reason for the upgrade, but nice to know it still works in mainline).