Cache files downloaded by download_weekly_pointing_file

[dstansby]

Describe the performance issue

sunkit_instruments.fermi.download_weekly_pointing_file doesn't cache the files it downloads, instead downloading a fresh copy each time it's called. e.g. calling it twice with the same date downloads identical files to different folders:

(sunpy) 🐊 dstansby@Davids-MBP sunkit-instruments % python test.py
/var/folders/m4/v0b71w0s22z34l90psw9j82w0000gn/T/tmp41ub2_7t/lat_spacecraft_weekly_w604_p310_v001.fits
(sunpy) 🐊 dstansby@Davids-MBP sunkit-instruments % python test.py
/var/folders/m4/v0b71w0s22z34l90psw9j82w0000gn/T/tmpklqmgxz9/lat_spacecraft_weekly_w604_p310_v001.fits

It would be good if these files were cached to prevent extra downloads.

To Reproduce

import sunpy

sunpy.map.Map(...)
etc

Proposed fix

No response

[wtbarnes]

Better yet, we should just be using the data manager (https://docs.sunpy.org/en/stable/how_to/remote_data_manager.html) and deprecate this function entirely.