Consistent File Access (using pathlib.Path instead of os.path)

We use both os and pathlib libraries for reading/writing files. I’d like to fix up the code to use either or. We can have a discussion on which is better here, but it seems a bit weird having two libs in that do the same thing

[fenhl]

For example, this line: https://github.com/mtgjson/mtgjson-python/blob/8666ea0e10c152e97936c2440857512604e10f79/mtgjson4/mtg_http.py#L135

could be rewritten as:

if (mtgjson4.mtg_storage.CACHE_DIR / 'set_mids' / f'{set_name}.txt').exists():

[ZeldaZach]

Sounds like a solid argument to me.

Ticket update: Move away from os.path -> pathlib.Path