With the old approach, we had to enumerate all StatusContexts and
CheckRuns to calculate whether a PR has passing or failing CI status.
Using `statusCheckRollup` which is behind the `pe_mobile` feature flag,
this is somewhat simpler because both StatusContexts and CheckRuns are
now behind the same connection.
Additionally, should we decide to *not* show the number of
passing/failing checks, this now approach allows us to consume the
`statusCheckRollup { state }` field and avoid paginated collections
and calculating the "winning" state altogether.
When an error occurs anywhere in a command, Cobra used to print the
error itself and command usage help.
We already print error in `main()`, and we don't want to use command
usage string on anything other than flag-parsing errors.
This also fixes the double output of each error.
