Pass WebSocket `connectionParams` to downstream also in `connectionParams`

[enisdenjo]

Continuation task of #4040.

Currently the WebSocket connectionParams are spread to request headers and passed through the extensions field of GraphQL request parameters. This is a tad confusing, see #4040 (comment).

Instead, it would be great if we could make the connectionParams be in connectionParams downstream.

[ardatan]

You probably already know that but I am adding this just to clarify the issue; GraphQL Mesh's runtime has nothing to do with HTTP actually, because the runtime only generates a schema (and an executor), then that schema/executor is used as a standalone artifact, an SDK or by an HTTP server(Yoga, Apollo etc).
We don't forward HTTP requests as they are in GraphQL Mesh, because the consumer might not be an HTTP server.

Then how can we pass connectionParams from the gateway to the underlying WS sources?
We can basically have an additional field in the configuration like operationHeaders that passes connectionParams dynamically to graphql-ws client.

connectionParams:
    x-foo: `some-static-prefix-{context.connectionParams['my-foo']}` # String interpolation