`EXPECT_...` statements can be used inside matcher definitions – this is an important option that is glossed over in this documentation. Users should definitely be aware of this option, since writing custom messages to the `result_listener` can be very cumbersome (and unnecessary) sometimes.
This change adds a relevant example and includes the associated error message it provides on failure.
PiperOrigin-RevId: 630206661
Change-Id: Idee00ba77ce3c1245597aa082f9cd0efff16aceb