rename post_process to finish_eager_conversion

[kroening]

This renames a set of solver methods from post_process to
finish_eager_conversion. The term 'post processing' may be used either in
lazy or eager solving. The new name clarifies that this is about an eager
conversion.

• Each commit message has a non-empty body, explaining why the change was made.
• n/a 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

Merging #6551 (72d0ed0) into develop (e4c5999) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff            @@
##           develop    #6551   +/-   ##
========================================
  Coverage    75.98%   75.98%           
========================================
  Files         1578     1578           
  Lines       181058   181058           
========================================
  Hits        137579   137579           
  Misses       43479    43479           

Impacted Files	Coverage Δ
src/goto-cc/gcc_cmdline.cpp	74.80% <ø> (ø)
src/solvers/flattening/bv_pointers.h	100.00% <ø> (ø)
src/solvers/prop/prop_conv_solver.h	42.85% <ø> (ø)
src/solvers/refinement/bv_refinement.h	83.33% <ø> (ø)
src/solvers/flattening/arrays.h	93.75% <100.00%> (ø)
src/solvers/flattening/boolbv.h	62.50% <100.00%> (ø)
src/solvers/flattening/boolbv_quantifier.cpp	90.90% <100.00%> (ø)
src/solvers/flattening/bv_pointers.cpp	83.06% <100.00%> (ø)
src/solvers/flattening/equality.h	88.88% <100.00%> (ø)
src/solvers/lowering/functions.h	50.00% <100.00%> (ø)
... and 3 more

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[tautschnig]

Just curious: this used to be protected. Why is making it public the right thing to do?

[kroening]

Yes, I am thinking about the use of this for an eager conversion, say to Dimacs, or something else.
Right now, we trigger the "finishing" by calling dec_solve, which then doesn't actually do solving, but returns an error, which we then ignore. It would be clearer to feed the constraints to the decision procedure, and then call finish_eager_conversion, and then be done.