Feature Request: Hide schemas in the GUI

Is there a way to _hide_ schemas in the GUI? We have a Redshift cluster with a _lot_ of different schemas and we want to hide `test_*` schemas and a few other unwanted schemas in the GUI. It will be really nice to have an option in the preferences to hide unwanted schemas, since Postgres does not provide a way to apply permissions in a way that can hide schemas.

At the moment, all the schemas are visible and when the user clicks on one of them, it alerts them that they don't have permission to view it.

Start at the GUI schema list and preferences entry points described in the issue. Reproduce the behavior with a Redshift cluster containing test_* and inaccessible schemas; the work is done when unwanted schemas can be configured as hidden and the permission alert is avoided for them.

Written by the indexing model from the issue text.