fix: use rechunk on main branch pushes (mirrors main build pattern)

rechunk is the mechanism that transfers the image from root (sudo) storage
to user-accessible storage before Load Image runs. Setting rechunk: false
broke Load Image with 'image not known'. Mirror the main build pattern:
rechunk on non-PR events, skip on PRs.

Also revert unnecessary sudo podman save|load workaround.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: James Reilly

.github/workflows/build-gnome50.yml

@@ -31,7 +31,7 @@ jobs:
       image-name: bluefin
       tag-suffix: "50"
       gnome-version: "50"
-      rechunk: false
+      rechunk: ${{ github.event_name != 'pull_request' }}
       publish: ${{ github.event_name != 'pull_request' && github.ref == 'refs/heads/main' }}
 
   build-hwe:
@@ -42,5 +42,5 @@ jobs:
       tag-suffix: "50"
       gnome-version: "50"
       hwe: true
-      rechunk: false
+      rechunk: ${{ github.event_name != 'pull_request' }}
       publish: ${{ github.event_name != 'pull_request' && github.ref == 'refs/heads/main' }}

.github/workflows/reusable-build-image.yml

@@ -211,11 +211,6 @@ jobs:
           skip_compression: true
           version: ${{ env.CENTOS_VERSION }}
 
-      - name: Copy image to rootless storage
-        if: ${{ inputs.publish && !inputs.rechunk }}
-        run: |
-          sudo podman save "localhost/${IMAGE_NAME}:${DEFAULT_TAG}" | podman load
-
       - name: Load Image
         if: ${{ inputs.publish }}
         id: load