[python] Fix conditional fall-through in SOMAObject.open

[nguyenv]

Issue and/or context:

As reported internally, the pybind11 implemented SOMAObject.open contains a conditional fall-through as of #3402.

Changes:

Wrap the C++ call in try-catch block where SOMAObject::open should already throw an exception for unknown types. In the Pybind11 code, if the conditional falls through then trigger an assert for unreachable code.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.29%. Comparing base (8eed6dc) to head (87f4227).
Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3446      +/-   ##
==========================================
+ Coverage   86.22%   86.29%   +0.06%     
==========================================
  Files          55       55              
  Lines        6295     6305      +10     
==========================================
+ Hits         5428     5441      +13     
+ Misses        867      864       -3     

Flag	Coverage Δ
python	86.29% <ø> (+0.06%)	⬆️

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Components	Coverage Δ
python_api	86.29% <ø> (+0.06%)	⬆️
libtiledbsoma	∅ <ø> (∅)