misc/multistream-select: Implement simultaneous open extension

From the multistream-select 1.0 simultaneous open protocol extension
specification:

> In order to support direct connections through NATs with hole
punching, we need to account for simultaneous open. In such cases, there
is no single initiator and responder, but instead both peers act as
initiators. This breaks protocol negotiation in multistream-select,
which assumes a single initator.

> This draft proposes a simple extension to the multistream protocol
negotiation in order to select a single initator when both peers are
acting as such.

See libp2p/specs#196 for details.

This commit implements the above specification, available via
`Version::V1SimOpen`.

misc/multistream-select/Cargo.toml

@@ -14,6 +14,7 @@ bytes = "1"
 futures = "0.3"
 log = "0.4"
 pin-project = "1.0.0"
+rand = "0.7"
 smallvec = "1.6.1"
 unsigned-varint = "0.7"