Further CSPICE support, improved error handling

[attipaci]

• Improved error handling, printing CSPICE short error messages when debug mode is enabled.
• Added convenience functions to manage active kernels:
  • cspice_add_kernel() -- wraps the CSPICE furnsh_c() function with graceful error handling.
  • cspice_remove_kernel() -- wraps the CSPICE unload_c() function with graceful error handling.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.65%. Comparing base (51fadb0) to head (bda1586).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #89   +/-   ##
=======================================
  Coverage   99.65%   99.65%           
=======================================
  Files           8        8           
  Lines        2904     2904           
  Branches      561      561           
=======================================
  Hits         2894     2894           
  Partials       10       10           

Flag	Coverage Δ
unittests	99.65% <ø> (ø)

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