Support providing SQL query parameters to `run_sql`

### Is your proposal related to a problem?

I'd like to make use of Hasura's connection pooling to execute arbitrary administrative SQL. The [`run_sql` endpoint](https://hasura.io/docs/latest/api-reference/schema-api/run-sql/#schema-run-sql) seems well suited for this, except it doesn't seem to support SQL query parameters.

### Describe the solution you'd like

I'd like the `run_sql` arguments to accept an JSON object containing query parameters.

### Describe alternatives you've considered

An alternative at the moment would be attempting to construct the SQL string manually by escaping / sanitizing query parameters myself. However my reading on the subject indicates that this is dangerous, error prone, and not something that should generally be done.

Start with the linked run_sql API reference and trace how the endpoint currently accepts and executes its arguments. Define the JSON query-parameter shape and verify that parameterized SQL works through the endpoint without requiring manual SQL construction.

Written by the indexing model from the issue text.