[Feature] Benchmark napari versus brainmapper code

[alessandrofelder]

Is your feature request related to a problem? Please describe.
A user reports that running cellfinder through napari takes 2 days on their machine, but only 1 day through the brainmapper CLI. We should run some tests to see whether we can reproduce, and if so, get to the bottom of it and write a benchmark for this.

Could be related to reading arrays with dask versus numpy.

Describe the solution you'd like
Napari and brainmapper cell finding speeds should be approx. the same.