Add a side workspace, similar to those in VSCode and PyCharm, to pgAdmin 4.

[akshay-joshi]

Implement separate workspace for Query Tool, PSQL, Schema Diff, etc. Attached is the POC work done.

There are a couple of things that we need to check:

1. Persistent with the already opened tabs.
2. Drag and Drop objects in the Query Tool.
3. Classic UI vs New and their respective changes.
4. Open an empty query tool tab which is difficult as a part of POC at the moment.

SideWorkspace_POC.patch