- Linux: use --retry-on-http-error=503 instead of --retry-connrefused
  (the latter only handles TCP-level failures, not HTTP 503)
- Windows: remove quotes around URL so Docker ARG substitution works
  with the default cmd shell

Docker expands ${baseDownloadUrl} before passing to cmd /S /C, but
without quotes special characters in the URL can be misinterpreted
by cmd.exe, causing curl exit code 3 (URL malformed).

…UN on Windows)

Transient Docker daemon (connection refused) and HCS (CreateComputeSystem)
failures cause frequent Windows CI flakes. Wrap both Gradle steps in a
3-attempt retry loop with 10s backoff, only on windows-latest.

Transient Docker daemon (connection refused) and HCS (CreateComputeSystem)
failures cause frequent Windows CI flakes. Wrap both Gradle steps with a
retry script (3 attempts on Windows, 1 on Linux) to recover automatically.

Remove duplicated inline retry loops from Build and Test steps in favor
of the shared .github/scripts/retry.sh wrapper.

Wrap the Windows docker image builds in pr-smoke-test-servlet-images and
publish-smoke-test-servlet-images with retry.sh to handle transient
Docker/HCS failures.

Replace ADD (which has no retry support) with PowerShell
Invoke-WebRequest wrapped in a retry loop (5 attempts, 3s wait)
to handle transient HTTP failures like 503s.