Add C# bazel 8 tests.

PiperOrigin-RevId: 743669719

Author: deannagarcia

.github/workflows/test_csharp.yml

@@ -27,7 +27,7 @@ jobs:
       - name: Run tests
         uses: protocolbuffers/protobuf-ci/docker@v4
         with:
-          image: us-docker.pkg.dev/protobuf-build/containers/test/linux/csharp:7.1.2-3.1.415-6.0.100-d9624f2aa83cba3eaf906f751d75b36aacb9aa82
+        image: us-docker.pkg.dev/protobuf-build/containers/test/linux/csharp:8.0.1-3.1.415-6.0.100-b77fdae6d4771789dfc66a56bf8d806354e8011a
           credentials: ${{ secrets.GAR_SERVICE_ACCOUNT }}
           entrypoint: /bin/bash
           command: >-
@@ -43,7 +43,7 @@ jobs:
       - name: Run conformance tests
         uses: protocolbuffers/protobuf-ci/bazel-docker@v4
         with:
-          image: us-docker.pkg.dev/protobuf-build/containers/test/linux/csharp:7.1.2-3.1.415-6.0.100-d9624f2aa83cba3eaf906f751d75b36aacb9aa82
+         image: us-docker.pkg.dev/protobuf-build/containers/test/linux/csharp:8.0.1-3.1.415-6.0.100-b77fdae6d4771789dfc66a56bf8d806354e8011a
           credentials: ${{ secrets.GAR_SERVICE_ACCOUNT }}
           bazel-cache: csharp_linux
           bazel: test //csharp:conformance_test --action_env=DOTNET_CLI_TELEMETRY_OPTOUT=1 --test_env=DOTNET_CLI_HOME=/home/bazel
@@ -74,7 +74,7 @@ jobs:
       - name: Run tests
         uses: protocolbuffers/protobuf-ci/bash@v4
         with:
-          bazel-version: 7.1.2
+          bazel-version: 8.0.1
           credentials: ${{ secrets.GAR_SERVICE_ACCOUNT }}
           command: |
             dotnet build csharp/src/Google.Protobuf.sln