Kernel prepatch 6.9-rc1

The timer subsystem had a fairly big rewrite, to have per-cpu timer wheels to improve performance of timers, which can be a big deal particularly for networking. The other fairly notable core update is to the workqueue subsystem, where one notable addition is for BH workqueue support. That's notable mainly because it means we finally have a way away from tasklets. The tasklet interface has basically been deprecated for a long while, but we've never really had any good alternatives (with threaded interrupt handlers being one suggested use-case, but not realistic in many cases).