Allow integrated relay chain light client (#2270)

* Add embedded light client to cli

* Prepare for light-client-worker

* First working version

* Clean up

* Remove unwanted logs

* Simplify subscription code

* Let jsonrpsee handle rpc management

* Simplify implementation

* Reorganize crate structure

* Use relay chain arg chainspec for light-client

* Clean up command line

* Add light client worker file

* Use smoldot master to avoid wasmtime conflict

* Remove sleep

* Improve naming of cli option

* Remove conflict with `validator`

* Improve docs

* Update smoldot, remove unwanted change

* Apply suggestions from code review

Co-authored-by: Dmitry Markin <dmitry@markin.tech>

* Disable collation

* Reviewer comments

* Update smoldot and tokio-platform

* Update smoldot

* Update smoldot

* Adjust to new version

* Patch substrate

* Use constants

* Add readme entry, improve zombienet tests

* Apply suggestions from code review

Co-authored-by: Michal Kucharczyk <1728078+michalkucharczyk@users.noreply.github.com>

* Make execution mode an enum

* Update smoldot, remove substrate patch

* Update client/relay-chain-rpc-interface/src/rpc_client.rs

Co-authored-by: Michal Kucharczyk <1728078+michalkucharczyk@users.noreply.github.com>

* Reduce duplicate code

* Update smoldot

* Update smoldot

* Fix build

* Update smoldot

* Make platform compile

* Clean up dependencies

* Use crates.io instead of github for smoldot

* Apply suggestions from code review

Co-authored-by: Davide Galassi <davxy@datawok.net>

* Docs

* Improve docs

* Remove `RpcFrontend`

---------

Co-authored-by: Dmitry Markin <dmitry@markin.tech>
Co-authored-by: Michal Kucharczyk <1728078+michalkucharczyk@users.noreply.github.com>
Co-authored-by: Davide Galassi <davxy@datawok.net>