scalar function fixes in cyice

[AndrewAnnex]

fixes #569 allowing numpy scalars and 0-d arrays to be used correctly with _s functions in cyice.

fixes string inputs that could cause segfaults as 0-d arrays.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.61%. Comparing base (c8b6da4) to head (4e1986f).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff            @@
##             main     #571    +/-   ##
========================================
  Coverage   99.61%   99.61%            
========================================
  Files          18       19     +1     
  Lines       17981    18094   +113     
========================================
+ Hits        17911    18024   +113     
  Misses         70       70            

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