Revert multiprocessing changes

[dstansby]

This PR reverts changes made to multiprocessing in the detection code to eeffcb4. The goal here is to have a temporary fix for #73

Fixes #81

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change

Comparison is base (b31ff82) 99.13% compared to head (d92f054) 99.13%.

❗ Current head d92f054 differs from pull request most recent head 8c9aa7c. Consider uploading reports for the commit 8c9aa7c to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #84   +/-   ##
=======================================
  Coverage   99.13%   99.13%           
=======================================
  Files           9        9           
  Lines         231      231           
=======================================
  Hits          229      229           
  Misses          2        2           

Impacted Files	Coverage Δ
tests/tests/test_integration/test_detection.py	100.00% <100.00%> (ø)

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[adamltyson]

A quick test suggests this works fine (200GB dataset, Ubuntu machine with 64GB RAM). Memory usage peaked around 10GB.

[adamltyson]

Seems to be errors on macOS both locally and on CI. Not sure what the problem was. Locally (M1) I was getting file not found errors.

[dstansby]

Decided not to go forwards with this