* [utils]: use futures mpsc

Use futures::channel::mpsc as it's already brought in as dependency and to avoid bring
in tokio sync as an additional dependency.

* remove unused deps/code

* fix nit

* [utils]: future mpsc works without alloc.

* [http server]: future mpsc works without alloc.

* refactor benches

* start

* fix build: enable `raw value` feature serde_json

* start

* port it

* make tests compile

* fix bench

* fix bench

* introduce builder pattern

* tweaks

* remove unused code

* cleanup

* [http server]: configure tcp socket manually.

The major reason is to provide a uniform API with the WebSocket server to return the local address.

* remove unused deps

* [examples]: remove needless sleep

* chore: add docs and refactor noise.

* Update types/src/jsonrpc/error.rs

* http server use constants