Geo: Create a new `Migrate data` page
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### Problem to solve
We have two options for customers looking to migrate their GitLab data to new infrastructure - Geo and Backup/Restore.
The Geo use case is not currently documented but we do have an [issue](https://gitlab.com/gitlab-org/gitlab/-/issues/388863) to address this.
The backup/restore instructions are documents under the [migrated to a new server](https://docs.gitlab.com/ee/administration/backup_restore/index.html#migrate-to-a-new-server) section in the backup documents.
### Proposal
We should create a new page `Migrate data` and consolidate the documentation under this page presenting the reader with both Geo and backup/restore options along with the benefits and drawbacks of each approach.
### Who can address the issue
Anyone with knowledge of Geo and Backup/Restore.
epic