cpan: Fix module version extraction for some edge cases

CPAN API can return versions that are not of str type: either int or float.

When version equals 0, it means that version failed to be parsed by CPAN so we try to extract it from release name in that case.

Otherwise we ensure to convert the version to str type.

Related to #2833

Depends on !321 (closed)

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Migrated from D8648 (view on Phabricator)