🚀 Enhancement: Make migrations not block everything during the process

### 🔖 Enhancement description Make the migration procedure start migrating the first/most crucial elements (for example, recent active users, latest database documents, etc). And prevent it from blocking practically the entire instance (although some data could be missing, etc. during the migration, the app will still be somewhat usable as the latest things are available). An alternative could be a 0 downtime procedure, but it's more complex obviously. ### 🎤 Pitch Current migration procedure blocks the entire appwrite instance meanwhile the script is being run. This is not a problem in a small app, but if you have a chat-like or similar app where you have thousands of documents, each time it's needed to upgrade, a big disruption is caused leaving the users without access during several minutes. ### 👀 Have you spent some time to check if this issue has been raised before? - [X] I checked and didn't find similar issue ### 🏢 Have you read the Code of Conduct? - [X] I have read the [Code of Conduct](https://github.com/appwrite/.github/blob/main/CODE_OF_CONDUCT.md)