intrng: convert to using resource manager for interrupt numbers

[ehem_freebsd_m5p.com]

Summary

The kernel interrupt numbers do amount to a type of resource. As such
this is the forte of the resource manager code. This should open future
possibilities.

[ehem_freebsd_m5p.com]

For some interrupt controllers it makes sense to allocate a range of interrupt numbers, rather than allocating them individually every time an INTRNG source is allocated. Interrupt numbers for INTRNG look suspiciously like a resource, at which point placing them with the resource manager seems to make sense.

This is a WIP, I'm unsure of the implementation. Perhaps an interface needs to be proposed first.

[ehem_freebsd_m5p.com]

Huh, looking back at this I'm wondering why the mv_ap806 bits were needed.

I'm pretty sure the approach is correct. I think my evaluation of value was wrong though, from what I've seen most ARM/ARM64/RISC-V interrupt controllers would substantially benefit from an approach like this. Right now most controllers are allocating large arrays of intr_irqsrc structures which effectively replicate the purpose of irq_source in subr_intr.c. Add the ability to allocate ranges and most controllers could individually allocate intr_irqsrc structures instead of needing a large array.

[ehem_freebsd_m5p.com]

I think I've found a better way to address this. Alas tis a bunch of commits and the throughput for non-sponsored patches is atrocious.