Make machine types and available IDEs accessible via the API

[filiptronicek]

Is your feature request related to a problem? Please describe

Clients may want to have their own "start a workspace" experience. Practically speaking, for the https://github.com/gitpod-samples/Gitpod-Raycast-Extension, IDEs and machine types have to be hard-coded into the code to be able to start workspaces properly.

This though itself is problematic (not just because of the problems arising with maintaining) - for other installation hosts like in a Gitpod Dedicated scenario, these machine types just cannot be gotten.

Describe the behaviour you'd like

Two read-only API endpoints:

1. for listing all IDEs along with their versions (similar to what we implement in ide-service, but in the Public API) - getIDEOptions
2. for listing all machine types available on the install for the currently logged-in user - getSupportedWorkspaceClasses