Implement flux migrate command

The migrate command must be run before a Flux minor version upgrade.
The command migrates the Flux custom resources stored in Kubernetes etcd to their latest API version, ensuring the Flux components can continue to function correctly after the upgrade.

Signed-off-by: Stefan Prodan <stefan.prodan@gmail.com>

.github/workflows/e2e.yaml

@@ -238,6 +238,9 @@ jobs:
       - name: flux check
         run: |
           ./bin/flux check
+      - name: flux migrate
+        run: |
+          ./bin/flux migrate
       - name: flux version
         run: |
           ./bin/flux version