Motivation:
Implementation of WebSocketUtil/randomNumber is incorrect and might violate
the API returning values > maximum specified.
Modifications:
* WebSocketUtil/randomNumber is reimplemented, the idea of the solution described
in the comment in the code
* Implementation of WebSocketUtil/randomBytes changed to nextBytes method
* PlatformDependet.threadLocalRandom is used instead of Math.random to improve efficiency
* Added test cases to check random numbers generator
* To ensure corretness, we now assert that min < max when generating random number
Result:
WebSocketUtil/randomNumber always produces correct result.
Covers https://github.com/netty/netty/issues/8023
fa4e28ba1c