Split up pandas tests

[tomuben]

Background

The pandas tests take the most time during our CI.
We should split them up, especially https://github.com/exasol/script-languages/blob/master/test_container/tests/test/pandas/all/dataframe_memory_leak.py and https://github.com/exasol/script-languages/blob/master/test_container/tests/test/pandas/all/emit_dtypes_memory_leak.py.
There are two options:

1. Or we move those files into a separate folder and then adjust the ci.json for all Python flavors
2. We modify https://github.com/exasol/script-languages-container-ci and allow specification of single files in the ci.jsonand then adjust the ci.json for all Python flavors

Acceptance Criteria

The pandas tests should run in parallel and thus run faster.