implement transient moving-average thermal model

**New Feature**
Implement the [transient moving-average model proposed by Matt Prillman](https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=9095219)

**Describe the solution you'd like**
a new function `pvlib.temperature.prillman(times, ...)`

**Describe alternatives you've considered**
see also #1080 

**Additional context**
see https://github.com/NREL/ssc/issues/261