[WIP] Remove decorator and new updates

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Major work in progress, opening PR for tracking progress. Not yet fit for consumption -- please don't try and use / comment on this branch until I have finished and verified!

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On the todo list:

• [ ] add typehints and update all docstrings
• [x] add data_array set_return_space() method - try to get rid of a few cp.asarray calls. See if lazy loading is possible for this.
• [x] test_voyager with smaller gulps, and check that correct indexes are returned
• [ ] tech memo: profiling with pyinstrument, memory usage
• [ ] tech memo: new search plans: optimal + stepped
• [ ] tech memo: SNR calcs
• [ ] tech memo: new pipeline class
• [ ] add better bandpass removal methods
• [x] add ability to write config to JSON file via find_et()
• [ ] tidy up the unit tests
• [ ] setigen SNR tests

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I'm happy for this to be merged into main now. Still some items on the todo, will transfer over to issues 🗃️