CI: Sync branch and tag after release (#89967)

* Added `workflow_call` event to allow other workflows to invoke the "Create or update GitHub release"
* Added `dry_run` to `github-release.yml`
* Added `latest` to `release-pr.yml` which will cause the release PR to add a `release/latest` label.
* Removed unnecessary github app creation from github-release workflow and just used permissions.

.github/workflows/release-pr.yml

@@ -24,6 +24,14 @@ on:
         required: false
         default: false
         type: bool
+      latest:
+        required: false
+        default: false
+        type: bool
+
+permissions:
+  content: write
+  pull-requests: write
 
 jobs:
   create-prs:
@@ -31,12 +39,6 @@ jobs:
     runs-on: ubuntu-latest
     if: github.repository == 'grafana/grafana'
     steps:
-      - name: Generate token
-        id: generate_token
-        uses: tibdex/github-app-token@b62528385c34dbc9f38e5f4225ac829252d1ea92
-        with:
-          app_id: ${{ secrets.GRAFANA_DELIVERY_BOT_APP_ID }}
-          private_key: ${{ secrets.GRAFANA_DELIVERY_BOT_APP_PEM }}
       - name: Checkout Grafana
         uses: actions/checkout@v4
       - name: Configure git user
@@ -62,12 +64,24 @@ jobs:
       - name: Create PR without backports
         if: "${{ inputs.backport == '' }}"
         run: >
-          gh pr create --dry-run=${{ inputs.dry_run }} -B "${{ inputs.target }}" --title "Release: ${{ inputs.version }}" --body "These code changes must be merged after a release is complete"
+          gh pr create \
+            $( (( ${{ inputs.latest }} == "true" )) && printf %s '-l "release/latest"') \
+            --dry-run=${{ inputs.dry_run }} \
+            -B "${{ inputs.target }}" \
+            --title "Release: ${{ inputs.version }}" \
+            --body "These code changes must be merged after a release is complete"
         env:
-          GH_TOKEN: ${{ steps.generate_token.outputs.token }}
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
       - name: Create PR with backports
         if: "${{ inputs.backport != '' }}"
         run: >
-          gh pr create -l "backport ${{ inputs.backport }}" -l "product-approved" --dry-run=${{ inputs.dry_run }} -B "${{ inputs.target }}" --title "Release: ${{ inputs.version }}" --body "These code changes must be merged after a release is complete"
+          gh pr create \
+            $( (( ${{ inputs.latest }} == "true" )) && printf %s '-l "release/latest"') \
+            -l "backport ${{ inputs.backport }}" \
+            -l "product-approved" \
+            --dry-run=${{ inputs.dry_run }} \
+            -B "${{ inputs.target }}" \
+            --title "Release: ${{ inputs.version }}" \
+            --body "These code changes must be merged after a release is complete"
         env:
-          GH_TOKEN: ${{ steps.generate_token.outputs.token }}
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}