No longer actively open legacy substreams (#7076)

* Allow remotes to not open a legacy substream

* No longer actively open legacy substreams

* Misc fixes

* Line width

* Special case first protocol as the one bearing the handshake

* Legacy opening state no longer keeps connection alive

* Remove now-unused code

* Simplify inject_dial_upgrade_error

* [chaos:basic]

* [chaos:basic]

* [chaos:basic]