Follow-up from "feat: add useDocker configuration for workflow"

The following discussions from !2411 (merged) should be addressed:

• @viktomas started a discussion: (+2 comments)

  (non-blocking, follow-up) let's rename the property to gitlab.duo.workflow.useDocker. This is not blocking because we probably want to migrate the other two duoWorkflow properties to the same name so we can do all 3 in a follow up.

  We might get away without doing migrations (since this si only dogfooded), but if you want backwards compatibility, there is already existing migration logic.

  ---

  (blocking) Should we also add this property to the contribution points in package.json (api docs)?

• @viktomas started a discussion:

  (non-blocking, follow-up): Same as the other comments, I suggest we use the existing duo namespace for the duo features. (not a separate duoWorkflowSettings)

• @viktomas started a discussion:

  (non-blocking, fast follow-up) Can this property go into DuoConfiguration?

  In general, it would be great if we could group the properties by feature. e.g. ExtensionConfiguration.duo.workflow.useDocker.