improve compatibility with nodes that don't support Identify

Nobody has claimed this yet.

We have problems dealing with nodes that don't support Identify. We pretty much _assume_ that every node will support identify.

1. We can ask the peer store if a peer supports a certain protocol. This information is _exclusively_ fed in by Identify. This is problematic because application protocols won't know if a protocol is not supported because it was not in the Identify protocol list (which is a good indication that the peer actually doesn't support it) or because the peer didn't complete Identify with us. This will likely necessitate a refactor of the peer store API.
2. We should feed the information that a protocol is supported into the peer store, when we successfully complete the multistream negotiation of that protocol (this applies both to streams that we open and streams that we accept). That way, we'll learn over time which protocols are support by a peer, even if that peer doesn't provide that information in Identify.

Start by tracing the peer store API, Identify protocol handling, and multistream negotiation for both opened and accepted streams. Determine how protocol support is currently recorded and how missing Identify data is represented. Done means peers without Identify can still be queried reliably, and successful negotiations update supported-protocol information.

Written by the indexing model from the issue text.