Function pointer removal: argument conversion must use byte extract

[tautschnig]

Only POD can be handled via type casts, all other cases require
reinterpreting the byte sequence. For POD, the simplifier will clean up
the byte extract.

The same problem had already been fixed for goto-symex' function
argument conversion back in bb80cdc.

Co-authored-by: Celina G. Val [email protected]

Fixes: #6956

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• 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).
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[codecov]

Codecov Report

Merging #6959 (e4d7411) into develop (b5ab3a1) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff            @@
##           develop    #6959   +/-   ##
========================================
  Coverage    77.79%   77.79%           
========================================
  Files         1568     1568           
  Lines       180347   180350    +3     
========================================
+ Hits        140309   140312    +3     
  Misses       40038    40038           

Impacted Files	Coverage Δ
jbmc/src/janalyzer/janalyzer_parse_options.cpp	48.58% <ø> (ø)
src/goto-analyzer/goto_analyzer_parse_options.cpp	72.27% <ø> (ø)
src/goto-programs/remove_function_pointers.cpp	92.79% <100.00%> (+0.09%)	⬆️

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