feat: pull neuron ground truths from allen brain

[tlambert03]

this PR will add a new ground truth: neuronal morphology from allen brain. It does so without depending on allen_sdk (which had a lot of extraneous dependencies that we don't want to take on)

Screen.Recording.2024-06-06.at.8.45.02.PM.mov

[codecov]

Codecov Report

Attention: Patch coverage is 95.39749% with 11 lines in your changes missing coverage. Please review.

Project coverage is 85.86%. Comparing base (c3d2c72) to head (1d94993).
Report is 1 commits behind head on main.

❗ Current head 1d94993 differs from pull request most recent head 552421e

Please upload reports for the commit 552421e to get more accurate results.

Files	Patch %	Lines
src/microsim/_draw.py	78.26%	5 Missing ⚠️
src/microsim/allen/_swc.py	97.02%	3 Missing ⚠️
src/microsim/allen/_fetch.py	98.00%	2 Missing ⚠️
src/microsim/util.py	88.88%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #48      +/-   ##
==========================================
+ Coverage   84.92%   85.86%   +0.93%     
==========================================
  Files          47       50       +3     
  Lines        2474     2702     +228     
==========================================
+ Hits         2101     2320     +219     
- Misses        373      382       +9     

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