add documentation for guidelines when migrating on-premise file blobstores into cloud

Users want to move their existing on-premise Repo 3 instance with large amounts of data already in blobstores into the cloud ( AWS, Azure, GCP, etc. ) in the most efficient manner possible and in the way that Sonatype recommends.

Expected

Provide a document that explains the various options pros and cons of each on how to do this for each major cloud platform and target storage type ( ie. S3, EBS, etc.)