Include tests from reported issue cbmc#5952.

[NlightNFotis]

This is including two tests from #5952,
one of which succeeds demonstrating that the issue is now fixed,
and the other one is failing, marked so as broken-smt-backend, presumably
because of the __CPROVER_r_ok within an assume context.

• 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 #6212 (e409ce2) into develop (0a0a862) will decrease coverage by 0.09%.
The diff coverage is 89.65%.

@@             Coverage Diff             @@
##           develop    #6212      +/-   ##
===========================================
- Coverage    75.20%   75.11%   -0.10%     
===========================================
  Files         1458     1458              
  Lines       161311   161402      +91     
===========================================
- Hits        121318   121230      -88     
- Misses       39993    40172     +179     

Impacted Files	Coverage Δ
src/goto-instrument/code_contracts.h	95.83% <ø> (ø)
src/goto-programs/goto_convert_class.h	87.30% <ø> (ø)
src/solvers/smt2/smt2_conv.h	100.00% <ø> (ø)
src/solvers/smt2/smt2_dec.h	100.00% <ø> (ø)
src/solvers/smt2/smt2_conv.cpp	67.18% <50.00%> (+0.64%)	⬆️
src/goto-programs/goto_convert.cpp	91.76% <90.00%> (+0.06%)	⬆️
src/goto-instrument/code_contracts.cpp	86.56% <91.11%> (+0.20%)	⬆️
src/solvers/flattening/boolbv.cpp	80.63% <100.00%> (ø)
src/solvers/prop/prop_conv_solver.cpp	88.18% <100.00%> (ø)
src/solvers/smt2/smt2_dec.cpp	71.42% <100.00%> (ø)
... and 19 more

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