Fix QRandomGenerator initialization on AMD CPUs

Some AMD CPUs (e.g. AMD A4-6250J and AMD Ryzen 3000-series) have a
failing random generation instruction, which always returns
0xffffffff, even when generation was "successful".

This code checks if hardware random generator can generate four
consecutive distinct numbers. If it fails the test, then we probably
have a failing one and should disable it completely.

Gerrit review:
https://codereview.qt-project.org/c/qt/qtbase/+/272837

BUG:411081