Remove DS command

[Mab879]

Keeping the code around as it used in other places in OpenSCAP.

Closes #2086

[jan-cerny]

You will have to do something with failing CTest tests. Some of them will have to be removed, some of them will have to be changed so that they don't use the oscap ds subcommand.

For example, I suggest changing tests/bz2/test_bz2_datastream.sh so that it doesn't compose the data stream during the test but instead it evaluates a static data stream stored in the repository (you can use the removed command oscap ds sds-compose to generate the data 🙉 ).

[Mab879]

Closing in favor of #2127