Add shadow memory set_field operation

[esteffin]

PR adding supoport for shadow memory __CPROVER_set_field function.
As for the __CPROVER_get_field code is experimental and will be improved in subsequent PRs

• 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.

[NlightNFotis]

Flag doesn't exist yet, should be left FUTURE now.

[esteffin]

Removed

[codecov]

Codecov Report

Patch coverage: 77.11% and project coverage change: +0.66% 🎉

Comparison is base (74f6669) 78.19% compared to head (a3964fe) 78.85%.
Report is 27 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #7846      +/-   ##
===========================================
+ Coverage    78.19%   78.85%   +0.66%     
===========================================
  Files         1698     1699       +1     
  Lines       195117   195222     +105     
===========================================
+ Hits        152566   153937    +1371     
+ Misses       42551    41285    -1266     

Files Changed	Coverage Δ
src/goto-symex/shadow_memory_util.cpp	81.21% <73.33%> (+19.95%)	⬆️
src/goto-symex/shadow_memory.cpp	90.41% <83.72%> (-0.50%)	⬇️

... and 86 files with indirect coverage changes

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