Adds bulk project repository storage move API

What does this MR do?

Fixes #272554 (closed)

Fixes #227833 (closed)

• Add a new API to bulk schedule a move for all projects on a storage shard.
• Not providing a destination will follow the new project storage selection ratios

Manual Testing

Setup gdk.yml:

praefect:
  enabled: true
gitaly:
  storage_count: 4

Rejigger gdk:

$ gdk reconfigre
$ gdk restart

Check where some project is currently stored so we know we'll move at least one:

$ curl -H "PRIVATE_TOKEN: XXXX" http://gdk.test:3000/api/v4/projects/19 | jq
{
  "id": 19,
...
  "repository_storage": "gitaly-3",
...
}

Reconfigure repository weights:

Initiate the move:

$ curl -X POST -H "PRIVATE_TOKEN: XXXX" -H "Content-Type: application/json" -d '{"source_storage_name": "gitaly-3"}' http://gdk.test:3000/api/v4/project_repository_storage_moves | jq
{
  "message": "202 Accepted"
}

After enough time, check that the project moved:

$ curl -H "PRIVATE_TOKEN: XXXX" http://gdk.test:3000/api/v4/projects/19 | jq
{
  "id": 19,
...
  "repository_storage": "gitaly-1",
...
}

🎉 🎉 🎉

Database

One iteration query:

SELECT "projects".* FROM "projects" WHERE "projects"."id" IN (SELECT "project_repositories"."project_id" FROM "project_repositories" WHERE "project_repositories"."shard_id" = 122 AND "project_repositories"."project_id" >= 16267295 AND "project_repositories"."project_id" < 16277136) 

Plan: https://explain.depesz.com/s/Zxlh

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team