[Dashboard] Document the usage of the che-server API

[ibuziuk]

Is your task related to a problem? Please describe

Currently, the dashboard is the only component that uses che-server REST API. The vast majority of the endpoints are not used anymore with the DevWorkspace flow, and will be removed in the upcoming versions of the project see:

• [Dashboard] Remove dependency on Workspace API provided by che-server #21846
• [Dashboard] Remove dependency on Devfile API provided by che-server #21845

As part of this issue in the the-dashboard README.md we need to document which endpoints are still used and are not planned to be deprecated e.g. factory / kubernetes-namespace

Describe the solution you'd like

README.md should contain a section with info about the che-server endpoints that are still used

Describe alternatives you've considered

N/A

Additional context

No response

[ibuziuk]

@azatsarynnyy @svor @tolusha folks, could you please confirm that the dashboard is the only operand that still uses Che-Server API

[azatsarynnyy]

@ibuziuk None of the Che-Server APIs are used by the Che editors: Theia, IDEA, VS Code.

[tolusha]

chectl uses system/state request to check che-server state.
But it can be easily removed