Pointer casting regression tests for new SMT backend

[NlightNFotis]

This is adding some tests to gauge the level of support we currently have for the conversion of casting of pointers in the new SMT backend.

More tests to come, but draft for now so that we can get some internal reviews first.

• Each commit message has a non-empty body, explaining why the change was made.
• 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).
• My PR is restricted to a single feature or bugfix.
• White-space or formatting changes outside the feature-related changed lines are in commits of their own.

[codecov]

Codecov Report

Merging #6923 (126cfff) into develop (4790e60) will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           develop    #6923      +/-   ##
===========================================
+ Coverage    77.79%   77.83%   +0.03%     
===========================================
  Files         1568     1569       +1     
  Lines       180295   180354      +59     
===========================================
+ Hits        140258   140374     +116     
+ Misses       40037    39980      -57     

Impacted Files	Coverage Δ
...c/solvers/smt2_incremental/convert_expr_to_smt.cpp	88.32% <100.00%> (+0.52%)	⬆️
...t/solvers/smt2_incremental/convert_expr_to_smt.cpp	99.66% <100.00%> (ø)
src/analyses/locals.h	85.71% <0.00%> (-14.29%)	⬇️
src/solvers/smt2/smt2_dec.cpp	73.27% <0.00%> (-3.92%)	⬇️
jbmc/src/jdiff/jdiff_parse_options.cpp	66.66% <0.00%> (-0.69%)	⬇️
jbmc/src/jbmc/jbmc_parse_options.cpp	76.06% <0.00%> (-0.35%)	⬇️
...lvers/strings/string_constraint_generator_main.cpp	81.37% <0.00%> (-0.32%)	⬇️
jbmc/src/janalyzer/janalyzer_parse_options.cpp	48.58% <0.00%> (-0.16%)	⬇️
...solvers/strings/string_format_builtin_function.cpp	72.93% <0.00%> (-0.13%)	⬇️
src/solvers/lowering/byte_operators.cpp	92.60% <0.00%> (-0.11%)	⬇️
... and 52 more

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[thomasspriggs]

Looks like this just needs clang-formatting.