symtab2gb should populate configt

[tautschnig]

For as long as goto-programs/ uses util/c_types.h, expression types
generated during goto-program construction rely on bit widths to be
configured.

• Each commit message has a non-empty body, explaining why the change was made.
• n/a Methods or procedures I have added are documented, following the guidelines provided in CODING_STANDARD.md.
• 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).
• n/a My commit message includes data points confirming performance improvements (if claimed).
• My PR is restricted to a single feature or bugfix.
• n/a White-space or formatting changes outside the feature-related changed lines are in commits of their own.

[codecov]

Codecov Report

Merging #5956 (64a7ca9) into develop (4c58926) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff            @@
##           develop    #5956   +/-   ##
========================================
  Coverage    74.23%   74.23%           
========================================
  Files         1431     1431           
  Lines       155291   155293    +2     
========================================
+ Hits        115287   115289    +2     
  Misses       40004    40004           

Impacted Files	Coverage Δ
src/symtab2gb/symtab2gb_parse_options.cpp	60.65% <100.00%> (+1.33%)	⬆️

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[martin-cs]

Definitely.