#168: Imlemented injection of external test container via CLI

[tomuben]

fixes #168

• [x] Implemented injection of TestContainer via API
• [x] Marked API functions which have a CLI equivalent and such which have not (for consistency tests)
• [x] Remove upload of artifacts to test container (UploadExaJDBC, and PopulateTestData)
• [x] Use exaplus within database container for checking status of db
• [x] Changed implementation of UploadFileToDB so that it uses exasol_bucketfs_utils_python instead of curl in test-container
• [x] Added a new container for creating the certificates
• [x] Add a new test for Upload
• [x] Adjusted existing tests to use new API call to inject Test-Container (where needed)
• [x] Add a new test for PopulateData
• [x] Add tests for TestContainer mapping (Build- and Run-time) - [ ] Remove unused buckets from EXAConf => #253
• [x] Restructure Tests such that it becomes clearer which tests use CLI and which use API
• [x] Cleanup Github workflows regarding test-container

Topics to discuss:

• [x] luigi does not allow an optional JsonPickleParameter, so I identifiy an empty TestContainerContentDescription when the dockerfile is None. Not ideal! => Decision to change implementation of JsonPickleParameter so that it can handle None.
• [x] CreateSSLCertificatesTask uses a temporary directory to extract the docker content temporarily. Would it be better to use the jobs cache directory? => Decision to keep current implementation.

All Submissions:

• [x] Is the title of the Pull Request correct?
• [x] Is the title of the corresponding issue correct?
• [x] Have you updated the changelog?
• [x] Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• [x] Are you mentioning the issue which this PullRequest fixes ("Fixes...")
• [x] Before you merge don't forget to run all tests for all Exasol version, by adding [run all tests] to the commit message