temperature: add support for fan and power readings

[umtdg]

What does this PR do?
Add support for fan and power readings to the temperature module.

Instead of adding custom modules for my cpu & gpu fan readings and gpu power readings, i was experimenting if i could just add this to the existing temperature module as it already does the heavy lifting by parsing the hwmon path and reading the file.

I've been using my branch for around ~9-10 months now with this config and this config. This was meant to be a quick stitch up at the time and can probably be done better. Any suggestion or anything that i missed in testing/documentation is welcome.

I could only test this on Linux and i don't have the knowledge or environment to implement this for FreeBSD and test.

Related issues
Closes #4681

Checklist

• Code is formatted with clang-format
• Builds locally (ninja -C build)
• Man page updated for any new/changed user-facing option (man/)
• Tested against the affected module(s)