CI/CD - Merge cuda12.9 images. (#728)

**Description**
Merge ARM64 and AMD64 images into a single multi-architecture Docker
manifest under one artifact namespace.
Co-authored-by: Hongtao Zhang <hongtaozhang@microsoft.com>

.github/workflows/build-image.yml

@@ -185,6 +185,11 @@ jobs:
           sources: >-
             superbench/main:cuda12.8-amd64
             superbench/main:cuda12.8-arm64
+        - name: cuda12.9
+          tags: superbench/main:cuda12.9
+          sources: >-
+            superbench/main:cuda12.9-amd64
+            superbench/main:cuda12.9-arm64
     steps:
     - name: Checkout
       uses: actions/checkout@v4