Develop tests for prov module

[emiliom]

• From @lsetiawan in PR Fix WindowsPath error with compute_Sv when run on Windows #829: I realized that we don't have a test for the utils/prov.py, maybe this will be great for our testing creation session in the future 😄
• From @emiliom in PR Handle xml_path in EchoData provenance on open_raw and combine_echodata #814: While creating this PR and Turn filenames dimension into coordinate variable #806, I've thought about tests. There are no tests (I think) that check for the correct creation of these file provenance variables. More broadly, I don't think we do much testing on provenance values, and that's probably a tricky area. Rather than trying to create very narrow tests in this PR, I think we should have a broader discussion. Maybe that could be folded into provenance work in 0.6.4.

[leewujung]

This is related to #1043 and #1042.

[emiliom]

See also the new issue #1050