Add teardown_actions (remove pipeline, remove index) and add to benchmark cli

[mathislucka]

• Check out the benchmark/runner package: src/deepset_mcp/benchmark/runner
• look at setup_actions.py and cli.py
• we want to add teardown_actions (remove index and pipeline) and also add these as commands to the cli
• look at src/deepset_mcp/api/pipeline/resource.py to see the signature for deleting a pipeline
• look at src/deepset_mcp/api/indexes/resource.py to see the signature for deleting an index

Generally follow the same code structure as in the setup_actions.

Only implement the changes that I'm asking for!

Raise a PR once you are done and satisfied with the quality of your code.