Drop submodule support

[spenserblack]

See #174 for context.

To do

• Simplify code

---

For #174

[codecov]

Codecov Report

Merging #175 (972be75) into main (df86f2b) will increase coverage by 2.64%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #175      +/-   ##
==========================================
+ Coverage   82.72%   85.37%   +2.64%     
==========================================
  Files          14       14              
  Lines         579      540      -39     
==========================================
- Hits          479      461      -18     
+ Misses        100       79      -21     

Flag	Coverage Δ
	85.37% <100.00%> (+2.64%)	⬆️
macOS-latest	84.94% <100.00%> (+2.27%)	⬆️
ubuntu-latest	81.64% <100.00%> (+2.15%)	⬆️
windows-latest	79.73% <100.00%> (+2.27%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
gengo/src/analysis/mod.rs	90.90% <100.00%> (+11.59%)	⬆️
gengo/src/lib.rs	91.58% <100.00%> (+10.29%)	⬆️

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