* Validate ansible-base & collection's runtime.yml
Add new test `runtime-metadata`
* Schema validation of file
* Error if a a legacy meta/routing.yml exist in a collection
* removal_date OR removal_version
* Add tombstone validation.
* Allow both ISO 8601 date strings and datetime.date objects (from YAML dates).
* Address review comments.
* Add metadata to test collection.
* Add requirements file.
Co-authored-by: Felix Fontein <felix@fontein.de>
Co-authored-by: Matt Clay <matt@mystile.com>
