Better Full Backup Migration documentation

[shaqaruden]

Based on this page https://develop.sentry.dev/self-hosted/backup/

There needs to be work completed to add proper documentation on how to migrate a sentry instance from one server to another. I have spent hours today trying to get this working but simply saying "follow docker documentation" is not enough to complete the process and leaves the user on how to migrate each individual piece of the stack on their own.