Support exec/attach calls

Exec and Attach class are non-standard calls that kubernetes API server uses to connect to a port of a pod/container or execute a command on them. It uses SPDY or WebSockets. Normal calls to these endpoints will result in an upgrade request from API server. We need to support WebSocket for this client (for those endpoints). [This is python](https://github.com/kubernetes-client/python-base/tree/a41c44715241552de73361673152f3f0d0bb9bc4/stream) implementation of the same feature.

Start by reading the Python reference implementation in the stream directory, then inspect this Haskell client's handling of Kubernetes API calls for the exec and attach endpoints. Done means those endpoints can establish and use WebSocket connections instead of failing on the API server's upgrade request.

Written by the indexing model from the issue text.