Use "long-wave" rather than "infra-red" to refer to thermal radiation.

[adriesse]

Describe the bug
Thermal radiation is referred to as "infra-red" or "ir" in two contexts (maybe more):

• faiman_rad temperature model
• surfrad.py

It would be preferable to standardize on "longwave" or "lw".

[kandersolar]

+1 from me. A bit of relevant discussion here: #2572 (comment)

[AdamRJensen]

I am in favor of writing out "longwave" instead of abbreviating it.

[Rahi-padwal]

Hello,
I would like to work on this issue and update the terminology to use “longwave” consistently.
Can i work on it?

[AdamRJensen]

This PR as it should be addressed by someone who's familiar with pvlib.