This patch tackles two things at once that are fairly intertwined:
1. There is no such thing as a "substream" in libp2p, the spec and other implementations only talk about "streams". We fix this by deprecating `NegotiatedSubstream`.
2. Previously, `NegotiatedSubstream` was a type alias that pointed to a type from `multistream-select`, effectively leaking the version of `multistream-select` to all dependencies of `libp2p-swarm`. We fix this by introducing a `Stream` newtype.
Resolves: #3759.
Related: #3748.
Pull-Request: #3912.
Previously, a protocol could be any sequence of bytes as long as it started with `/`. Now, we directly parse a protocol as `String` which enforces it to be valid UTF8.
To notify users of this change, we delete the `ProtocolName` trait. The new requirement is that users need to provide a type that implements `AsRef<str>`.
We also add a `StreamProtocol` newtype in `libp2p-swarm` which provides an easy way for users to ensure their protocol strings are compliant. The newtype enforces that protocol strings start with `/`. `StreamProtocol` also implements `AsRef<str>`, meaning users can directly use it in their upgrades.
`multistream-select` by itself only changes marginally with this patch. The only thing we enforce in the type-system is that protocols must implement `AsRef<str>`.
Resolves: #2831.
Pull-Request: #3746.
* Simplify trait bounds requirements
* More work
* Moar
* Finish
* Fix final tests
* More simplification
* Use separate traits for Inbound/Outbound
* Update gossipsub and remove warnings
* Add documentation to swarm
* Remove BoxSubstream
* Fix tests not compiling
* Fix stack overflow
* Address concerns
* For some reason my IDE ignored libp2p-kad
