sim: disambiguate duplicate names of traced signals

[wanda-phi]

Fixes #976.

[codecov]

Codecov Report

Attention: 6 lines in your changes are missing coverage. Please review.

Comparison is base (ef5cfa7) 84.00% compared to head (f611f0a) 83.95%.
Report is 2 commits behind head on main.

Files	Patch %	Lines
amaranth/sim/pysim.py	14.28%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #980      +/-   ##
==========================================
- Coverage   84.00%   83.95%   -0.05%     
==========================================
  Files          55       55              
  Lines        8053     8061       +8     
  Branches     1963     1965       +2     
==========================================
+ Hits         6765     6768       +3     
- Misses       1076     1080       +4     
- Partials      212      213       +1     

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