[Fix] Search system paths for shared libraries

[benniekiss]

This PR implements using ctypes.util.find_library to find the shared library paths while still falling back to the manual path searching logic.

This improves support for libraries which are installed into standard locations, or which appropriately install themselves with the correct linker targets.

Closes #63

[JamePeng]

If you are using AI programming, it's best to validate it locally before submitting a pull request.

[benniekiss]

I did not have AI weite this, I just did not run the test suite locally. I did test the change locally, and it worked. I'll check what's going wrong here...

[benniekiss]

Tests pass locally. The issue was a missing import statement.

[benniekiss]

I'm closing this for now, as the library-search is still failing in my case. I believe I must have had a hardcoded path when I initially tested this that allowed the library to load correctly.

Apologies for the bother!

[benniekiss]

Ok, I have this straightened out now -- I had unset DYLD_LIBRARY_PATH. Resetting allows the package to load with this PR, otherwise, the env var paths are never searched. This PR makes it respect both DYLD_LIBRARY_PATH and LD_LIBRARY_PATH.