[$] The long road to lazy preemption

The kernel's CPU scheduler currently offers several preemption modes that
implement a range of tradeoffs between system throughput and response time.
Back in September 2023, a discussion
on scheduling led to the concept of 'lazy preemption', which could
simplify scheduling in the kernel while providing better results. Things
went quiet for a while, but lazy preemption has returned in the form of this patch series
from Peter Zijlstra. While the concept appears to work well, there is
still a fair amount of work to be done.