helper function for validating a counterparty upgrade against the selfupgrade

[charleenfei]

In reference to this suggestion:

    err := k.checkUpgradesForCompatibility(proposedUpgrade, counterpartyUpgrade)
    if err != nil {
        return types.NewUpgradeError(channel.UpgradeSequence, err)
    }

Originally posted by @colin-axner in #3671 (comment)

[colin-axner]

Also see comment here for potential names of the three types of valdiation

[crodriguezvega]

Closed by #4016.