Integrate tower::Service into client infrastructure

[pscoro]

Description

In order to provide middleware (in particular for telemetry), we want to make use of tower::Service in our clients. We intend to wrap http and grpc client implementations each in tower services and enable middleware such as tower_http::TraceLayer to be used.

Acceptance Criteria

• All http and grpc clients are layered tower services
• the client services properly support http, grpc, streaming and middleware while using tower
• client invocation is updated to execute through service.call()
• helper functions are added to http/grpc clients to simplify tower service calls