Ability to disable migrations and changing DB schema from the Hasura Console

### Is your proposal related to a problem?

Because Hasura's migration system doesn't apply multiple migrations transactionally and generally isn't as nice as purpose-built migrations tools, my company has decided to use other tools to manage our migrations. See https://github.com/hasura/graphql-engine/issues/7166

But since the Hasura Console lets you by default modify the database schema in the UI however you like, we just have to tell our engineers to "pretty please don't touch that", which isn't great.

### Describe the solution you'd like

Some configuration to disable the ability to mutate the database schema directly in the UI. Instead we want to handle migrations separately, then just use `hasura metadata reload` to ensure that changes are present in the UI.

### Describe alternatives you've considered

Making Hasura's migration system better, but given that Hasura intentionally made the system worse over 2 years ago and still hasn't fixed the regression, probably an uphill battle to convince the team that that was a mistake.

The issue names no files or tests. Start by reviewing the Hasura Console controls for direct database-schema changes and existing configuration options, then verify that the proposed setting blocks those changes while `hasura metadata reload` still refreshes the UI.

Written by the indexing model from the issue text.