Console: create a `Config` trait that aliases the Allow RO/Allow RW/Subscribe config traits.
Console: create a `Config` trait that aliases the Allow RO/Allow RW/Subscribe config traits.

Currently, the `console` API only writes `platform::allow_ro::Config + platform::allow_rw::Config + platform::subscribe::Config` twice. However, when I introduce the async APIs, I will be duplicating that trait bound several times. This PR makes an alias for that combination of traits, to avoid code repetition when I introduce async APIs.

tock/libtock-rs