transport: Optimize protocol name construction on every every substream open

[lexnv]

Litep2p constructs a list of protocols (including name and fallback) to negotiate with the remote peer.
This list can be statically constructed since the protocol names are not supposed to change.

litep2p/src/transport/s2n-quic/connection.rs

Lines 169 to 174 in e0b7118

	// TODO: protocols don't change after they've been initialized so this should be done only
	// once
	let protocols = std::iter::once(&*protocol)
	.chain(fallback_names.iter().map(|protocol| &**protocol))
	.collect();