Fix Create Table From Scratch on schema page

[seancolsen]

We need to finish implementing the tables.add RPC API across the stack.

On the schema page, we have a "New Table" dropdown button with a "From Scratch" option. When the user selects this option Mathesar should create a new table, automatically assigning it a name.

Currently, the table is created successfully, but the API does not return information about the name. We should change the API return type from a simple OID value to a JSON object containing the OID and name. We discussed this return type in our 2024-07-23 Technical Beta Planning meeting, and agreed on the above plan.

After the API return value is updated, then the front end needs to make use of the returned name, setting up the table object in the front end store appropriately.

This should be a very small amount of work, both on the back end and the front end.