Fix --nondet-static-exclude to handle symbol names and report errors

[tautschnig]

--nondet-static-exclude previously silently failed or crashed when using certain variable name formats.

Fixes: #8225

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• n/a The feature or user visible behaviour I have added or modified has been documented in the User Guide in doc/cprover-manual/
• Regression or unit tests are included, or existing tests cover the modified code (in this case I have detailed which ones those are in the commit message).
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[codecov]

Codecov Report

❌ Patch coverage is 76.92308% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 79.94%. Comparing base (4fe3ade) to head (33306c4).

Files with missing lines	Patch %	Lines
src/goto-instrument/nondet_static.cpp	76.92%	3 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #8752   +/-   ##
========================================
  Coverage    79.93%   79.94%           
========================================
  Files         1698     1698           
  Lines       187698   187707    +9     
  Branches        73       73           
========================================
+ Hits        150034   150054   +20     
+ Misses       37664    37653   -11     

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