Add support for ACPI thermal control to power_profile

[crahman_gmail.com]

Summary

The acpi_thermal module provides support for thermal regulation using ACPI and
various ACPI-defined thresholds, such as _PSV, _CR3, _HOT, and _CRT.

The correct setting of these thresholds may depend upon the A/C power condition;
fans might be more useful while A/C power is present, passive cooling more useful
without A/C power.

The acpi_thermal module resets the values of these thresholds to the ACPI defaults
after each A/C power transition, and they should be reset to appropriate values
after these events.

Using power_profile provides a flexible means of implementing various thermal and power
managment strategies that are appropriate for different hardware configurations.

Test Plan

Set the desired configuration up by editing /etc/rc.conf and disconnecting/reconnecting
A/C power.

[crahman_gmail.com]

Having this work spread between different patches for such a long time has made it hard for me to track and maintain it. I'm going to merge it with D35704.