Move Remote Dev settings back to EE

Issue: Move Remote Dev settings back to EE (#473201)

What does this MR do and why?

Moves Remote Development Settings module out of CE and back to EE (where it previously was).

Background

We had initially decided that Web IDE and Workspaces would share the settings module, since a couple of the VS Code related settings were shared. So in this MR (TODO: add link), we moved the settings module to CE.

However, as things evolve, we realize this would make it more complicated to evolve the settings module for workspaces, and the CE/EE split would create a lot of otherwise-unnecessary code and work, just to support two shared Web IDE/Workspaces settings. Also, this approach somewhat violated the CE/EE boundary by putting some EE-only settings on the CE side.

With Move extensions marketplace settings to webide ... (!157999 - merged), the shared VS-Code specific settings have been moved to the Web IDE domain, with its own dedicated instance/implementation of the settings module, and Workspaces can just directly reference and use the shared VS Code settings from there.

That all unblocked this MR, which moves all the remaining Workspaces-only settings back to the Remote Development domain under EE.

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

No UI changes, all backend.

How to set up and validate locally

All Workspaces functionality should work with no regressions:

• scripts/remote_development/run-smoke-test-suite.sh should pass locally
• scripts/remote_development/run-e2e-tests.sh should run locally (ensure there are no "spinning" workspaces or it will fail)
• CI should pass, including with pipeline:run-as-if-foss label set
• Local exploratory test of basic workspace functionality should work
  • create/use/terminate a workspace
  • Ensure agent admin workspaces list works