Unify API between single and multi hypothesis segmentations

[cmalinmayor]

Proposed Change

• Assume that segmentations always have t, h, [z], y, x
• Add ability to create final segmentation from selected graph and multihypothesis input segmentaiton
  Note: This is breaking for the candidate graph creation API (need to add channel/hypothesis dim to segmentation input)

Checklist

Go through these things before merge. Actions should run automatically to test them, but for information on how to run locally, see CONTRIBUTING.md.

• I have added tests that prove that my feature works in various situations or tests the bugfix (if applicable).
• I have checked that the tests pass and I maintained or improved test coverage (if applicable).
• I have written docstrings and checked that they render correctly in the documentation build.
• I have checked that mypy type checking passes.