`catalyst.pipeline` fixes

[paul0403]

Context: Two fixes on catalyst.passes.pipeline:

1. Moved to top level, so now also available as catalyst.pipeline
2. No need to specify the argument name, i.e. catalyst.pipeline({...})(qnode_func) now works (as opposed to catalyst.pipeline(pass_pipeline={...})(qnode_func) )

[github-actions[bot]]

Hello. You may have forgotten to update the changelog! Please edit doc/releases/changelog-dev.md on your branch with:

• A one-to-two sentence description of the change. You may include a small working example for new features.
• A link back to this PR.
• Your name (or GitHub username) in the contributors section.