Protocol Buffer support

The format is described here: https://developers.google.com/protocol-buffers/

There is already an implementation of protobuf generator for Qt here: https://github.com/semlanik/qtprotobuf , it is done bu semlanik. It also includes client-side support for GRPC. The current license is MIT, so compatible with Qt.

As far as I can see, the project provides tools for generating code from proto files, and 2 libraries to support protobuf and gRPC usage (see also QTBUG-98029) that need to be linked into applications, there is also CMake code to help to integrate everything into application.

There are some things that need to be done before this can be integrated in Qt, but that doable:

• CMake usage need to be updated to current standards
• Changes needed to how QtNetwork API is used
• Qt6 need to be supported

Additionally tests and examples need to be update. Documentation need to be integrated into the rest of Qt documentation.