Actually run tests

[tomaskontrimas]

Currently the only workflow that runs tests is started manually here:
https://github.com/icecube/i3skyllh/blob/master/.github/workflows/analysis_unittests.yml

We should review and run tests using pytest or unittest

[chiarabellenghi]

Running skyllh/tests/run.sh returns

..........ssh: Could not resolve hostname cobalt: nodename nor servname provided, or not known
rsync(28373): error: unexpected end of file
rsync(28373): error: io_read_nonblocking
rsync(28373): error: io_read_buf
rsync(28373): error: io_read_int
rsync(28373): warning: child 28375 exited with status 255

There is an attempt to fetch some test data from the cobalts. Do we really need this? Can't this data be stored within SkyLLH itself if it is a small sample for a functionality test only?