[Epic] Support MessagePack Hub Protocol in SignalR Java Client

[analogrelay]

We should add support for MessagePack to the SignalR Java Client.

This will require:

• [SignalR] Identify a suitable MessagePack library for the Java client to use #21107 Identifying and evaluating MessagePack libraries for Java
• Add MessagePack support for the Java SignalR Client #21644 Building a Hub Protocol implementation for Java according to the spec (https://github.com/dotnet/aspnetcore/blob/master/src/SignalR/docs/specs/HubProtocol.md)
• Adding functional tests for Java (we don't have any right now :S) to cover this and other scenarios like JSON. Not part of this work item