refactor: move stream upgrades to libp2p-swarm

[thomaseizinger]

Description

In #4307, we introduced dedicated traits for connection upgrades. This was to separate the concept of stream and connection upgrades. The next logic step is to move all existing stream upgrades to libp2p-swarm. Utilities like ReadyUpgrade or DeniedUpgrade are only ever used by ConnectionHandler implementations. Thus, there is no need for them to reside in libp2p-core.

On the surface, this looks like a really big change but this is only because these types are used in a lot of places. Moving them to libp2p-swarm allows us to remove the UpgradeInfoSend, InboundUpgradeSend and OutboundUpgradeSend types because we simply apply the Send bounds directly to the traits themselves.

Within libp2p-swarm, we also know that these traits are only ever called with a Stream as a socket which allows us to remove the C type parameter from them.

At the same time, we can remove the P type parameter from types like ReadyUpgrade by always specifying it as a StreamProtocol.

Related: #2863.
Resolves: #4697.

Notes & open questions

Change checklist

• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• A changelog entry has been made in the appropriate crates

[thomaseizinger]

I am setting this to draft for now. I don't want to block the release on it. Whilst I think this particular step is going in the right direction, I want to experiment with a few more APIs before making such an impactful change.