`http_client` and `http_server` docs about their metadata is wrong

[mfelsche]

Both expect and emit metadata under $http_server or $http_client prefixes. The section about metadata https://www.tremor.rs/docs/0.12/reference/connectors/http#metadata needs an overhaul in that regard.

How the server handles response metadata under $http_server.response can be seen by following this piece of code: https://github.com/tremor-rs/tremor-runtime/blob/main/src/connectors/impls/http/server.rs#L537
This is how the server represents request metadata underneath $http_server.request.

This is how the http_client connector extracts http request properties from the event metadata below $http_client.request: https://github.com/tremor-rs/tremor-runtime/blob/main/src/connectors/impls/http/meta.rs#L55
This is how the http_client connector represents response data under $http_client.response: https://github.com/tremor-rs/tremor-runtime/blob/main/src/connectors/impls/http/meta.rs#L315-L321