Need to fix version v1alpha1 of devfile API

[amisevsk]

Is your feature request related to a problem? Please describe.

Recent discussions around issues such as #102 has brought forward the realization that we haven't actually fixed the devfile spec for v1alpha1 and it is still possible to merge breaking changes there. This is an issue because this API is already consumed by the devworkspace operator and the OpenShift console, though this usage is a fairly minimal subset of the spec:

kind: DevWorkspace
apiVersion: workspace.devfile.io/v1alpha1
metadata:
  name: web-terminal
  annotations:
    controller.devfile.io/restricted-access: "true"
  labels:
    console.openshift.io/terminal: "true"
spec:
  started: true
  routingClass: 'web-terminal'
  template:
    components:
      - plugin:
          name: web-terminal
          id: redhat-developer/web-terminal/4.5.0

Having conflicting specs with the workspace.devfile.io/v1alpha1/DevWorkspace GVK will make it impossible to use v1alpha1, and any breaking changes that aren't compatible with the yaml above will break the devworkspace operator in a way that's not easily fixed, since it likely isn't possible to migrate between specs within the same GVK.

Describe the solution you'd like

We need to fix v1alpha1 as soon as possible, and push any not-backwards-compatible changes to a v1alpha2 or v1beta1 version instead.