Apply release fallback to datastreams validation

[jsoriano]

#785 deprecated the release label and added fallbacks to keep populating
it to maintain backwards compatibility in APIs.

This fallback was not added to package validation, making it fail when the
release label is not present in package and data stream manifests.

Temporary solution till we implement #626.

[elasticmachine]

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• Start Time: 2022-04-04T15:45:53.773+0000

• Duration: 5 min 51 sec

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