Add a factory link parameter to specify the editor

Synced from Eclipse Che issue

https://github.com/eclipse/che/issues/20508

Is your enhancement related to a problem? Please describe

Today, with DevWorkspaces, when selecting a default stack we can't select another editor than the default one.

As we've more and more editors and project is being cloned, we may want to have to select the IDE that we want as the default one.

Describe the solution you'd like

In user preferences page, be able to have a list of available editors and be able to choose the one that we want.

Then when opening the getting started examples, this editor will be pickup.

I don't know if we can provide through factory the editor that we may want as well ?
like http://che-server#https://github.com/eclipse/che&editor=che-theia

Describe alternatives you've considered

Small icons on every tiles of the Getting Started stacks (one for each available editor)

Additional context

Maybe when we connect the first time on Dashboard we should be prompted to configure the editor that we want.

Or connect to github to get token.

Release Notes Text

A user can specify a particular editor to use as a factory link parameter. For example, to use Che-Theia, http://che-server#https://github.com/eclipse/che?che-editor=eclipse/che-theia/latest.