Solver factory: all solvers are stack_decision_proceduret

[tautschnig]

There is no need for both get_decision_procedure and get_stack_decision_procedure where the latter uses dynamic_cast.

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• 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.
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[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 3 lines in your changes missing coverage. Please review.

Project coverage is 77.94%. Comparing base (b87d38a) to head (72e8727).
Report is 2 commits behind head on develop.

Files	Patch %	Lines
src/goto-checker/multi_path_symex_checker.cpp	50.00%	1 Missing ⚠️
...-checker/single_loop_incremental_symex_checker.cpp	75.00%	1 Missing ⚠️
src/goto-checker/single_path_symex_checker.cpp	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #8408      +/-   ##
===========================================
- Coverage    77.95%   77.94%   -0.02%     
===========================================
  Files         1726     1726              
  Lines       189601   189621      +20     
  Branches     18250    18247       -3     
===========================================
- Hits        147796   147792       -4     
- Misses       41805    41829      +24     

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[kroening]

Approving, but as a reminder, stack-based interfaces are obsolete, and I'd like to get rid of stack_decision_proceduret.

[peterschrammel]

stack-based interfaces are obsolete

Stack-based interfaces may be obsolete in the underlying solvers, but as a programming model to implement algorithms it is extremely convenient.