Create general script `mkdir_run.sh` to replace specific
scripts `extraction_eddies.sh`, `test_read_snapshot.sh`,
`test_read_eddy.sh` and to run `test_successive_overlap`.

Replace `$input_dir` by `$src_dir/Tests/Input` in
`*_tests.json`. Motivation: we also need `src_dir` to point to
`mkdir_run.sh`.