hrtimer: Re-arrange hrtimer_interrupt()

hrtimer: Re-arrange hrtimer_interrupt()

Rework hrtimer_interrupt() such that reprogramming is split out into an
independent function at the end of the interrupt.

This prepares for reprogramming getting delayed beyond the end of
hrtimer_interrupt().

Notably, this changes the hang handling to always wait 100ms instead of
trying to keep it proportional to the actual delay. This simplifies the
state, also this really shouldn't be happening.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260224163430.870639266@kernel.org