mas: Fix parsing on mas 3.0.0+. (#11179)
* mas: Fix parsing on mas 3.0.0+.
`mas` changed the formatting of `mas list` with version 3, which breaks
the parsing this module uses to determine which apps are installed. In
particular, app IDs may now have leading space, which causes us to split
the string too early.
* Changelog fragment.
* Better format examples and changlog fragment.
(cherry picked from commit ebb534166e)
a2042c9b93