Add support for dynamic object sizes in old smt decision procedure

[thomasspriggs]

This PR adds support for dynamic object sizes in old SMT backend. This fixes #7690

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• Methods or procedures I have added are documented, following the guidelines provided in CODING_STANDARD.md.
• 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).
• My commit message includes data points confirming performance improvements (if claimed).
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[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.21 🎉

Comparison is base (ce831a0) 77.59% compared to head (2fdec1a) 77.80%.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #7768      +/-   ##
===========================================
+ Coverage    77.59%   77.80%   +0.21%     
===========================================
  Files         1693     1693              
  Lines       193309   193308       -1     
===========================================
+ Hits        149997   150407     +410     
+ Misses       43312    42901     -411     

Impacted Files	Coverage Δ
src/solvers/smt2/smt2_conv.cpp	67.37% <100.00%> (-0.01%)	⬇️

... and 86 files with indirect coverage changes

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