asmc: replace hardcoded model table with universal probing

Probe SMC keys at attach time to detect hardware capabilities,
supporting all Intel Apple machines without per-model entries.

Sensors are discovered by scanning sorted SMC key ranges for
known prefixes and types. Capabilities such as SMS, fan safe
speed, and ambient light are detected by key presence.

A global key description table provides human-readable names
for well-known temperature sensors.

Tested on:

• MacBook Pro (Early 2007, Mid 2014, Mid 2015)
• MacBook Air (Early 2015, Mid 2017)
• iMac (Mid 2011, Late 2013)
• Mac mini (Mid 2011)

Reviewed by: adrian
Differential Revision: https://reviews.freebsd.org/D56405