Improve Multi Repositories Support

The multi repositories support within the Nuxeo Platform needs to be improved on some areas:

• Running an automation on multiple documents located in different repositories.
• Running a bulk command on multiple documents located in different repositories.

We also want to study some topics around multi repositories support such as:

• How to be able to restore only one repository in a multi repositories configuration - assuming we have a specific MongoDB collection, bucket, ES index for each repository. During the last POC, an issue was the need of reindexing all the repositories, not just the one restored: to be checked.
• Possibility of having repositories (data + blobs) stored in different regions.