Fix naming of npe1 converted contribution commands and add tests

[DragaDoncila]

Prior to this PR, declaring multiple implementations of the same hookspec in an npe1 plugin would lead to a converted manifest with multiple commands of the same ID e.g. plugin_name.get_reader multiple times, or plugin_name.write_labels multiple times.

Even though this is technically "valid" per the schema, it should not be, because this leads to errors in trying to register the commands in napari. App-model (correctly, imo), does not allow you to register multiple commands with the same ID.

We should update the schema validator to disallow multiple declarations of the same command ID, but in the meantime, this PR disambiguates converted commands for the same hook spec by using the function name instead of the spec name.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (c536e39) to head (7ba08e8).
Report is 1 commits behind head on main.

Additional details and impacted files

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  Coverage   100.00%   100.00%           
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  Files           37        37           
  Lines         2711      2711           
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  Hits          2711      2711           

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[jni]

wow, nice find 😵