Add global transport-level filters #761
Description
This would be a follow up to #733 that adds 11 different filter types for different client-to-server RPC types. A "global" filter could continue to be limited to these type of requests but simply handle all of them using a base type to RequestContext<TParams>, but I think the better approach would be to allow you to write a filter that can intercept and potentially forward or modify any incoming or outgoing JsonRpcMessage.
This would allow the global filter to see all messages including notifications, which could be particularly useful for diagnostics, but it would not be able to as easily match requests with responses withough tracking IDs. This could potentially be useful for the client as well.