pcp

Make Linux interrupt metrics use dynamic names.

Switch kernel.percpu.interrupts metric which used the combined
CPU and interrupt-line instance domain to be individual percpu
metrics (CPU indom) with separate namespace entries for each
interrupt line.

Also, we add here all the missing metrics from /proc/interrupts

• counters (e.g. on x86) for non-maskable interrupts, performance monitoring interrupts, rescheduling interrupts, TLB shootdowns, etc as well as the count of interrupt handling errors.