[Due for payment 2025-06-05] [Desktop Navigation] Remove the workspace switcher and its associated unused code entirely

[mountiny]

Part of https://github.com/Expensify/Expensify/issues/468845

Implement this section of the Design doc (linking to the tasks section as this project is being handled by SWM).

Issue Owner

Current Issue Owner: @NicMendonca

[melvin-bot]

Triggered auto assignment to @NicMendonca (NewFeature), see https://stackoverflowteams.com/c/expensify/questions/14418#:~:text=BugZero%20process%20steps%20for%20feature%20requests for more details. Please add this Feature request to a GH project, as outlined in the SO.

[WojtekBoman]

Hey, I'm going to work on it