Rename UPLC goldens to have file extension `.uplc`

[SeungheonOh]

Thanks to @rvcas, we have language support to uplc now natively on github! We can change all golden files with extension *.uplc.golden to *.golden.uplc to take advantage of github syntax highlighting and language recognition.

We also want other files like *.pir.golden to also be renamed to *.golden.pir for consistency.

[Unisay]

We have a few ways to render UPLC to text:

Name	Description
classic	Lisp-like syntax with unique variable names (default)
classic-simple	Lisp-like syntax with ambiguous (no unique) variable names
readable	Succinct syntax with unique variable names
readable-simple	Succinct syntax with ambiguous (no unique) variable names

What exactly is supported by Github?

[SeungheonOh]

It appears it's classic, which is what's used in the UPLC spec itself