otioconvert to OTIOZ fails with relative media target_urls

[jminor]

Description

otioconvert fails to convert OTIO to OTIOZ if there are media target_urls which start with "./"

Related bug: #1783

Reproduction Steps

1. Download the attached OTIO and media file.
2. Run this command:

% uvx --from opentimelineio otioconvert -i time_warp_test.otio -o time_warp_test.otioz

Log output if appropriate

Traceback (most recent call last):
  File "/Users/jminor/.cache/uv/archive-v0/egUCtOWX8VKGzLpjlRQw-/bin/otioconvert", line 10, in <module>
    sys.exit(main())
  File "/Users/jminor/.cache/uv/archive-v0/egUCtOWX8VKGzLpjlRQw-/lib/python3.8/site-packages/opentimelineio/console/otioconvert.py", line 273, in main
    otio.adapters.write_to_file(
  File "/Users/jminor/.cache/uv/archive-v0/egUCtOWX8VKGzLpjlRQw-/lib/python3.8/site-packages/opentimelineio/adapters/__init__.py", line 203, in write_to_file
    return adapter.write_to_file(
  File "/Users/jminor/.cache/uv/archive-v0/egUCtOWX8VKGzLpjlRQw-/lib/python3.8/site-packages/opentimelineio/adapters/adapter.py", line 189, in write_to_file
    result = self._execute_function(
  File "/Users/jminor/.cache/uv/archive-v0/egUCtOWX8VKGzLpjlRQw-/lib/python3.8/site-packages/opentimelineio/plugins/python_plugin.py", line 144, in _execute_function
    return (getattr(self.module(), func_name)(**kwargs))
  File "/Users/jminor/.cache/uv/archive-v0/egUCtOWX8VKGzLpjlRQw-/lib/python3.8/site-packages/opentimelineio/adapters/otioz.py", line 93, in write_to_file
    result_otio, path_to_mr_map = utils._prepped_otio_for_bundle_and_manifest(
  File "/Users/jminor/.cache/uv/archive-v0/egUCtOWX8VKGzLpjlRQw-/lib/python3.8/site-packages/opentimelineio/adapters/file_bundle_utils.py", line 132, in _prepped_otio_for_bundle_and_manifest
    target_file = os.path.abspath(url_utils.filepath_from_url(target_url))
  File "/Users/jminor/.cache/uv/archive-v0/egUCtOWX8VKGzLpjlRQw-/lib/python3.8/site-packages/opentimelineio/url_utils.py", line 75, in filepath_from_url
    elif PureWindowsPath(filepath.parts[1]).drive:
IndexError: tuple index out of range

Sample data and other attachements

otioconvert_relative_paths_to_otioz_bug_repro.zip