acpi_gpiobus: Enumerate GPIO interrupt pins and wire up cousin interrupts

[obiwac]

Summary

During _CRS enumeration, record GPIO interrupt pins (pin number, flags,
consumer ACPI handle) instead of just setting pin flags. This defers
interrupt setup until we know which consumers exist.

After enumeration, iterate over discovered interrupt pins and use the
acpi_cousin_intr mechanism to connect them to their consumers.

Sponsored by: The FreeBSD Foundation

[obiwac]

this is very not done!