ICS4: Channel Upgradability Spec (#677)

* copy over connection upgrade spec and replace connection with channel

* do core changes, TODO: app changes and callbacks

* fix typos

* call app upgrade callbacks

* fix restoreChannelUnless usage

* fix state conditional checks on TRY

* Apply suggestions from code review

Co-authored-by: colin axnér <25233464+colin-axner@users.noreply.github.com>

* fix partial review of colin, left out crossing hello remarks

* Apply suggestions from code review

Co-authored-by: Marius Poke <marius.poke@posteo.de>

* fix verify functions

* consistent msg names

* add explicit erroring

Co-authored-by: colin axnér <25233464+colin-axner@users.noreply.github.com>
Co-authored-by: Marius Poke <marius.poke@posteo.de>