Move the legacy protocol handshake to the legacy substream (#5938)

* Move the legacy protocol handshake to the legacy substream

* Fix tests

* Remove line that wasn't supposed to be committed

* Remove hack

* Rework how it's done

* Some little changes

* update_chain wasn't doing its thing

* Fix service tests not calling update_chain

* Update client/network/src/protocol/generic_proto/behaviour.rs

Co-authored-by: Max Inden <mail@max-inden.de>

* [WIP]

* Revert "[WIP]"

This reverts commit 2b892e6a7637c0b1297e6ecdbb919321c9098ff5.

* Update client/network/src/protocol.rs

Co-authored-by: Max Inden <mail@max-inden.de>

* Fix received message not being handshake

* Update client/network/src/protocol/generic_proto/behaviour.rs

Co-authored-by: Max Inden <mail@max-inden.de>

Co-authored-by: Max Inden <mail@max-inden.de>