Allow users to close a schema treeview node in the data manager

### Is your proposal related to a problem?

When exploring the schemas and tables in the data manager view, you can open a schema and see the tables that are below. But you cannot close it again. This is counter intuitive since most treeviews allow you to expand and collapse a treeview node

### Describe the solution you'd like

When a user clicks a treeview node that is already open, it should collapse again.

### Describe alternatives you've considered

none


Start at the data manager view's schema and table treeview entry point and reproduce the current expand behavior. Trace how an already-open schema node is handled on click, then verify that clicking it again collapses the node while preserving expansion of other nodes.

Written by the indexing model from the issue text.