Employ Protobuf in Clients/GUI section of data exchange

[xjules]

Based on to the successful performance measurement tests https://github.com/equinor/ert/issues/3581 and once https://github.com/equinor/ert/issues/3616 is completed, Protobuf data format should be employed for the client / GUI end of the experiment server communication protocol.

We should take the following issue (ie. running exp. server next to QT) into consideration https://github.com/equinor/ert/issues/3443 . For completeness, the Protobuf dispatcher PR is here: https://github.com/equinor/ert/pull/3620