Replaced sequential HTTP POST requests with `asyncio.gather` for the
Cloudflare upload speed test in `tier_cloudflare`. This allows payloads
to be uploaded concurrently, significantly improving the upload
throughput measurement (observed increase from ~15 Mbps to ~33 Mbps in
benchmarks) and reducing total test duration.
Co-authored-by: Horizontal42 <75383519+Horizontal42@users.noreply.github.com>
