pg_untrack_function does not persist

### Version Information

Server Version:
CLI Version (for CLI related issue): 2.0.7

### Environment

docker

### What is the expected behaviour?

Calling the `/v1/metadata` to track a function should persist it in the schema. It does not make sense to have to run the curl command each time the Hasura instance starts again, especially on production.

### Keywords

pg_untrack_function

### What is the current behaviour?

Function is tracked but disappears when server is restarted.

### How to reproduce the issue?

1. Send the request to `http://localhost:8080/v1/metadata`
```json
{
"type": "pg_track_function",
"args": {
"function": {
"schema": "public",
"name": "me"
},
"source": "default",
"configuration": {
"session_argument": "hasura_session"
}
}
}
```
2. Restart server
3. Tracked function is gone

### Any possible solutions?

Have the tracked function being written into metadata on file system.

Start by tracing the /v1/metadata pg_track_function request and the metadata loaded during server startup. Reproduce the issue with the provided request, restart the Hasura instance, and verify that the tracked function persists afterward.

Written by the indexing model from the issue text.