support non-versioned release files in the product-release finder

Some project release their files under the code name, not the version,. The product release finder cannot match these files to a version to pull add the files to a release.

lib/lp/registry/scripts/productreleasefinder/finder.py could be smarter.
The extract_version() returns early because there is no parsable version.
We could have a get_version_from_code_name() function that
    * Creates a match pattern from the series milestone code_names
    * If there is a match on the file path, use the code_name's version
    * return the version

The extract_version() could fallback to get_version_from_code_name if the version is none.