Use cmdlinet::get_comma_separated_values where possible

[tautschnig]

This is to make sure we accept repeat use of command-line options the
arguments of which are comma-separated values.

• 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 #6996 (e12b764) into develop (917f9a0) will increase coverage by 0.01%.
The diff coverage is 46.66%.

@@             Coverage Diff             @@
##           develop    #6996      +/-   ##
===========================================
+ Coverage    77.83%   77.84%   +0.01%     
===========================================
  Files         1569     1569              
  Lines       180624   180590      -34     
===========================================
- Hits        140583   140582       -1     
+ Misses       40041    40008      -33     

Impacted Files	Coverage Δ
jbmc/src/jbmc/jbmc_parse_options.cpp	75.88% <0.00%> (-0.18%)	⬇️
src/goto-harness/goto_harness_parse_options.cpp	78.09% <0.00%> (+9.76%)	⬆️
src/memory-analyzer/analyze_symbol.h	84.21% <ø> (ø)
.../memory-analyzer/memory_analyzer_parse_options.cpp	63.88% <40.00%> (+8.94%)	⬆️
src/cbmc/cbmc_parse_options.cpp	80.15% <100.00%> (+0.04%)	⬆️
.../goto-instrument/goto_instrument_parse_options.cpp	70.93% <100.00%> (+0.03%)	⬆️
src/goto-instrument/unwindset.cpp	85.43% <100.00%> (-0.42%)	⬇️
src/memory-analyzer/analyze_symbol.cpp	74.02% <100.00%> (+1.03%)	⬆️
... and 1 more

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[chris-ryder]

Looks great to me :-) With just one completely optional comment about how the PR/commit is described. With apologies again for the tardiness!

[chris-ryder]

Commenting here, but more a comment for the PR and/or commit descriptions... But I was having a slightly hard time groking the intent of this PR until I saw this example here in the test case 👍 - So perhaps a clearer description might be something like:

Allow command line options that take values consisting of comma separated list to be
repeated and accumulated into a single list. For instance, making `--foo A,B,C,D` be
semantically equivalent to `--foo A,B --foo C,D`

Or words to that affect... not sure if its clearer or not to other people... but at least having the example in the description would be a big help :-)

[tautschnig]

Thank you, I shamelessly copied this into the commit message!