Add migration handler to enable 09-localhost client and store sentinel connectionEnd

[damiannolan]

Summary

Add a migration handler for chain upgrades to enable the 09-localhost client and store a sentinel localhost connectionEnd in state.

1. Create the 09-localhost client and set in state using the 02-client keeper SetClientState
2. Create the sentinal localhost connectionEnd using the CreateLocalhost method added to 03-connection in Add sentinel localhost connectionEnd to genesis state #3031

This can be run as an automatic migration handler by bumping the core IBC module consensus version and registering a new migration in module.go.

err := cfg.RegisterMigration(exported.ModuleName, 3, m.Migrate3to4)
if err != nil {
	panic(err)
}

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