streams: close one-shot Identify and AutoNAT streams on every exit path

[adust09]

Affected protocols

• Identify request (/ipfs/id/1.0.0)
• AutoNAT v1 request/response (/libp2p/autonat/1.0.0)
• Potentially other one-shot handlers dispatched by the Switch

These exchanges complete after one response and must finish the Yamux stream lifecycle rather than leave a permanent half-open stream.

Current state

requestIdentify reads the framed response and returns without closing its local stream side. The responder does send FIN, leaving the initiator handle in a remote-half-closed state until it sends its own FIN.

AutoNAT's responder writes its response without closing, and requestAutoNAT also returns without closing.

Switch.Listen.dispatchStream releases the resource-manager stream reservation when a handler returns but does not close the actual stream. Thus accounting can say the stream was released while the Yamux session still retains it.

Scope

• Define clear stream ownership for StreamHandler: either every one-shot handler closes its stream, or dispatch provides a safe close-on-return policy with an explicit escape hatch for long-lived/handed-off streams.
• Close Identify initiator streams on success, negotiation rejection, decoding failure, and exceptions.
• Close both AutoNAT sides after their one-response exchange on all exit paths.
• Ensure close is idempotent and does not discard a response before it is flushed.
• Keep long-lived handlers (DHT, Ping sessions, relayed streams, GossipSub) working under the chosen ownership model.
• Align resource-manager release with actual stream termination.

Acceptance tests

• Repeated Identify requests return the Yamux stream map and resource usage to baseline.
• Repeated AutoNAT requests do the same on both peers.
• Decode/negotiation/error paths close or reset the stream.
• A handler that explicitly hands off a long-lived stream is not prematurely closed.
• Stream reservation counts match live Yamux streams after handler completion.