[release] Docker Release build trigger on rc for testing (#117849)

Enable triggering the Docker Release builds on RC. Use test channel in this case. Hence following logic is applied:
1. On RC trigger use test channel and upload to pytorch-test : https://github.com/orgs/pytorch/packages/container/package/pytorch-test
2. On Final RC use prod channel and upload to pytorch : https://github.com/orgs/pytorch/packages/container/package/pytorch
3. Nightly: https://github.com/orgs/pytorch/packages/container/package/pytorch-nightly

Pull Request resolved: #117849
Approved by: https://github.com/malfet

.github/workflows/docker-release.yml

@@ -11,8 +11,10 @@ on:
     branches:
       - nightly
     tags:
-      # We want to run this build on final release tag
+      # Final Release tags look like: v1.11.0
       - v[0-9]+.[0-9]+.[0-9]+
+      # Release candidate tags look like: v1.11.0-rc1
+      - v[0-9]+.[0-9]+.[0-9]+-rc[0-9]+
       - ciflow/nightly/*
 
 concurrency:
@@ -101,6 +103,16 @@ jobs:
           echo "${RUNNER_TEMP}/bin" >> "${GITHUB_PATH}"
           # Generate PyTorch version to use
           echo "PYTORCH_VERSION=$(python3 .github/scripts/generate_pytorch_version.py --no-build-suffix)" >> "${GITHUB_ENV}"
+      - name: Setup test specific variables
+        if: ${{ startsWith(github.event.ref, 'refs/tags/v') }}
+        run: |
+          if [[ ${{ github.event.ref }} =~ ^refs/tags/v[0-9]+\.[0-9]+\.[0-9]+-rc[0-9]+$ ]]; then
+            {
+              echo "DOCKER_IMAGE=pytorch-test";
+              echo "INSTALL_CHANNEL=pytorch-test";
+              echo "TRITON_VERSION=$(cut -f 1 .ci/docker/triton_version.txt)";
+            } >> "${GITHUB_ENV}"
+          fi
       - name: Setup nightly specific variables
         if: ${{ github.event.ref == 'refs/heads/nightly' || startsWith(github.event.ref, 'refs/tags/ciflow/nightly/') }}
         run: |