* make GetChannelByName take teamId first
I think it is more natural to accept `teamId`, then `channelName`,
given the pattern followed by other Plugin API methods and even the SQL
Store itself. The App layer seems unusual in accepting `channelName`
first.
This also re-generates the mocks fixing the parameter order for the
recently added `UserStatus` APIs.
* add GetChannelByNameForTeamName