Changing trigger back to workflow dispatch with reusable workflows

Reusable workflow call event type is the same as parent workflow.
So since server event is push, cascaded workflows also have event type as push.

Hence, adding workflow dispatch again which trigger the workflows in the other repos which themselves use reusable workflow.
Hopefully this marks event-type as workflow dispatch.
- Server workflow event would be push.
- Other repo workflow events would be dispatch.
    - These repos then call the reusable workflow which should have event type as dispatch.

.github/workflows/image_build_push.yml

@@ -4,6 +4,8 @@ on:
   push:
     branches: [ main, cleanup-cicd ]
 
+  workflow_dispatch:
+
 jobs:
   dump_contexts_to_log:
     runs-on: ubuntu-latest