syzbot: test more *-next branches

[dvyukov]

syzbot currently tests net-next and bpf-next. We probably should onboard more *-next trees. We need trees that are:

• not rebased (commit hashes work, bisection works)
• maintained in a reasonably good shape (no tons of assorted crashes)
• reasonably active (makes sense to test)
• merge upstream periodically (bugs are getting fixed)
• with maintainers who are willing to cooperate and fix bugs

[RonjaPonja]

not rebased (commit hashes work, bisection works)

We are trying to reconstruct new SHA1s based on the commit message now. Hopefully this should be good enough here.