change load_library to return the paths of files that failed to load

[airyclam]

This is related to issue #645 , where the user received error message

  File "/Users/<User>/opt/anaconda3/envs/<envname>/lib/python3.11/site-packages/wand/api.py", line 143, in load_library
    raise IOError('cannot find library; tried paths: ' + repr(tried_paths))

where tried_paths included a path with a library file. The root cause was that the file existed but could not be loaded as it was incompatible.

The new change includes in the error message that a file was found but was unable to be loaded correctly. This indicates to the user that they should check that file to make sure it's compatible with their system.

[Tsubashi]

Having run into this with users as well, this seems like a good idea.