goto-harness: use __CPROVER_(de)?allocate, not malloc/free

[tautschnig]

Do not use C-specific functions when amending GOTO programs.

Fixes: #8681

• 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.
• 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

Attention: Patch coverage is 94.59459% with 2 lines in your changes missing coverage. Please review.

Project coverage is 80.39%. Comparing base (d148ae6) to head (f06afc4).
Report is 3 commits behind head on develop.

Files with missing lines	Patch %	Lines
src/ansi-c/expr2c.cpp	90.00%	1 Missing ⚠️
src/goto-harness/recursive_initialization.cpp	96.29%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #8684      +/-   ##
===========================================
- Coverage    80.39%   80.39%   -0.01%     
===========================================
  Files         1688     1688              
  Lines       207392   207383       -9     
  Branches        73       73              
===========================================
- Hits        166739   166731       -8     
+ Misses       40653    40652       -1     

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[archigup]

Shouldn't this test pass?

[tautschnig]

Not in this restricted setting of that particular regression test as we don't actually do contracts instrumentation. The full workflow now does pass.