Windows: Ensure Docker engine is running

When running a swift_package_tests.yaml workflow, workflows running in a
docker container on windows would often fails as the docker engine was
not currently ready to accept requests.

Add a step that ensure the docker engine is ready, by calling `docker info`
before performing any other docker steps.

Author: bkhouri

.github/workflows/swift_package_test.yml

@@ -750,6 +750,30 @@ jobs:
           foreach ($line in $lines) {
               echo $line | Out-File -FilePath $Env:GITHUB_ENV -Encoding utf8 -Append
           }
+      - name: Ensure Docker engine is ready
+        if: ${{ inputs.enable_windows_docker }}
+        run: |
+          # Wait for Docker to be ready
+          $maxRetries = 30
+          $retryCount = 0
+          while ($retryCount -lt $maxRetries) {
+            try {
+              docker info | Out-Null
+              if ($LASTEXITCODE) {
+                throw "docker engine is not ready"
+              }
+              Write-Host "Docker engine is ready"
+              break
+            } catch {
+              $retryCount++
+              Write-Host "Waiting for Docker engine to be ready... ($retryCount/$maxRetries)"
+              Start-Sleep -Seconds 2
+            }
+          }
+          if ($retryCount -eq $maxRetries) {
+            Write-Error "Docker engine failed to start"
+            exit 1
+          }
       - name: Pull Docker image
         id: pull_docker_image
         if: ${{ inputs.enable_windows_docker }}