[DRAFT] Converter cleanup

[gramalingam]

Please do not review: just running CI for now.

[codecov]

Codecov Report

❌ Patch coverage is 87.50000% with 14 lines in your changes missing coverage. Please review.
✅ Project coverage is 70.11%. Comparing base (70e751a) to head (dbda8e4).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
onnxscript/converter.py	91.08%	5 Missing and 4 partials ⚠️
...ewriter/ort_fusions/fused_matmul_rule_sets_test.py	0.00%	3 Missing ⚠️
onnxscript/values.py	33.33%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2692      +/-   ##
==========================================
- Coverage   70.11%   70.11%   -0.01%     
==========================================
  Files         225      225              
  Lines       27068    27098      +30     
  Branches     2721     2731      +10     
==========================================
+ Hits        18980    19000      +20     
- Misses       7148     7155       +7     
- Partials      940      943       +3     

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