[RFE] improve aarch64 hinv.cpu metrics

[natoscott]

For hinv metrics on aarch64, particularly the CPU model / vendor / etc., only the hex IDs are reported. It'd be far more useful to present user-readable strings like on x86 platforms.

This will need some lookup tables in pmdalinux for aarch64 builds that provide correct strings based on the 'CPU implementer' and 'CPU part' fields. Here's the equivalent code in the (also GPL2+) util-linux package: https://github.com/util-linux/util-linux/blob/master/sys-utils/lscpu-arm.c

We'd need something similar, unfortunately there's no API for this so "manual" code sharing with util-linux is probably the best we can do.