Move "is hidden" attribute of goto functions out of type

[tautschnig]

Whether the execution of a goto function is to be hidden has nothing to
do with its signature, and therefore should not be included in the type
(irrespective of whether the type is stored in goto_functiont or in the
symbol table).

As this attribute is recomputed upon reading a goto binary, there is no
need to store it in the goto binary, and thus also no need to bump the
goto-binary version number.

The first commit in this PR is a clean revert of #4312.

• 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.
• n/a White-space or formatting changes outside the feature-related changed lines are in commits of their own.

[codecov]

Codecov Report

Merging #5575 (4e5bf6e) into develop (16ed35a) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff            @@
##           develop    #5575   +/-   ##
========================================
  Coverage    69.31%   69.31%           
========================================
  Files         1241     1241           
  Lines       100407   100406    -1     
========================================
+ Hits         69596    69599    +3     
+ Misses       30811    30807    -4     

Flag	Coverage Δ
cproversmt2	43.07% <85.71%> (-0.01%)	⬇️
regression	66.21% <100.00%> (+<0.01%)	⬆️
unit	32.27% <100.00%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/goto-programs/goto_convert_functions.cpp	100.00% <ø> (ø)
src/goto-programs/read_bin_goto_object.cpp	91.20% <ø> (-0.10%)	⬇️
src/util/symbol.h	94.44% <ø> (-0.16%)	⬇️
src/goto-instrument/cover_filter.cpp	60.00% <100.00%> (ø)
src/goto-programs/goto_function.h	95.45% <100.00%> (+1.01%)	⬆️
src/goto-programs/goto_inline_class.cpp	82.47% <100.00%> (ø)
src/goto-symex/symex_function_call.cpp	88.07% <100.00%> (-0.08%)	⬇️
src/goto-symex/symex_main.cpp	87.74% <100.00%> (-0.04%)	⬇️
src/solvers/strings/string_builtin_function.h	76.82% <0.00%> (+2.43%)	⬆️
src/solvers/flattening/pointer_logic.cpp	92.42% <0.00%> (+3.03%)	⬆️

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