rework files included in test folder

[Thomas Gilgenast]

we currently include several files in the tests/ directory in the lib5c repository that are used for testing purposes

this folder currently weighs in at nearly 200 MB

the files present are very confusing - it’s not clear which primermaps correspond to which countsfiles, or what the differences between the countsfiles are

this could probably be slimmed down to improve cloning speed by deleting or shrinking test files

making test files smaller may also significantly speed up the tests that interact with them

[Thomas Gilgenast]

as a more extreme step, we can consider removing the large files from the repo history

see https://stackoverflow.com/q/2100907 for example solutions

this would speed up cloning the full repository

an alternative is to make a shallow clone