[CI][v0.18.0] Build nightly image for releases/v0.18.0 per pr (#7662)

### What this PR does / why we need it?
This patch add per pr image build for branch `releases/v0.18.0`, Due to
the limitations of the quay naming convention, we should not name the
image tag the same as branch name, we name the image
tag`releases-v0.18.0` for daily build.

Signed-off-by: hfadzxy <starmoon_zhang@163.com>

.github/workflows/_schedule_image_build.yaml

@@ -47,6 +47,7 @@ jobs:
       with:
         fetch-depth: 0
         persist-credentials: false
+        ref: ${{ github.ref }}
 
     - uses: actions/checkout@v6
       if: ${{ github.event_name == 'workflow_dispatch' }}
@@ -113,6 +114,8 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v6
+        with:
+          ref: ${{ github.ref }}
 
       - name: Download arm64 digests
         uses: actions/download-artifact@v8
@@ -154,9 +157,9 @@ jobs:
           #      which follow the rule from vLLM with prefix v
           # TODO(yikun): the post release might be considered as latest release
           tags: |
+            type=ref,event=branch,suffix=${{ env.SUFFIX }}
+            type=ref,event=pr,suffix=${{ env.SUFFIX }}
             type=pep440,pattern={{raw}},suffix=${{ env.SUFFIX }}
-            type=schedule,pattern=main,suffix=${{ env.SUFFIX }}
-            type=raw,value=${{ inputs.workflow_dispatch_tag }},enable=${{ github.event_name == 'workflow_dispatch' }},suffix=${{ env.SUFFIX }}
           flavor:
             latest=false