change make_return method name and signature

[kroening]

The method creates a 'set return value' instruction, and the new name reflects that.

The method now takes the return value as argument, and not a code_returnt expression.

• 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).
• 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

Merging #6407 (4b740c2) into develop (cd36425) will increase coverage by 0.00%.
The diff coverage is 94.52%.

@@           Coverage Diff            @@
##           develop    #6407   +/-   ##
========================================
  Coverage    75.98%   75.98%           
========================================
  Files         1523     1524    +1     
  Lines       164275   164283    +8     
========================================
+ Hits        124830   124838    +8     
  Misses       39445    39445           

Impacted Files	Coverage Δ
src/ansi-c/c_typecheck_base.h	100.00% <ø> (ø)
src/goto-programs/goto_convert_class.h	87.30% <ø> (ø)
src/goto-symex/goto_symex.h	92.30% <ø> (ø)
src/goto-symex/symex_builtin_functions.cpp	93.60% <ø> (ø)
src/jsil/jsil_parse_tree.cpp	0.00% <0.00%> (ø)
src/jsil/jsil_typecheck.cpp	0.00% <0.00%> (ø)
src/jsil/jsil_typecheck.h	0.00% <ø> (ø)
unit/goto-programs/goto_program_validate.cpp	100.00% <ø> (ø)
src/goto-symex/symex_function_call.cpp	93.18% <88.00%> (ø)
src/util/std_code_base.h	93.54% <93.54%> (ø)
... and 23 more

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