Investigate overhead of QNetworkRequest/Reply + QNetworkAccessManager

A customer is concerning about the overhead of Qt Network. The test is like:
1. Send a HTTP PUT request to local/remote server (established by Python http.server) using Qt APIs
2. Send the same request to the same Python server using Python http.client module

Tried both 5.15.17 and 6.8.0 with release build as well as Python 3.12, and the result goes like:
1. With Qt5.15.17, time for getting a reply from local server is around 10ms, and 80ms from remote server.
2. With Qt6.8.0, it is around 15ms (slower somehow) for local server and 30ms for remote server.
3. With Python http.client.HTTPConnection, it takes almost no time (usually 0~1ms) for local server and 10ms for remote server.

Therefore, the concern is that:
1. It takes abnormally longer time to get a reply from remote server, especially for 5.15
2. Qt is much slower than Python

Test app with Python script for http server and client attached.