libtimeinstate: Print missing uid on test failure

AllUidTimeInStateMonotonic and AllUidConcurrentTimesMonotonic runs have
occasionally failed on this assertion, but without knowing which uid we
expect to find in the map, it is difficult to find the root cause. Print
the uid that we failed on for easier debugging.

Flag: TEST_ONLY
Bug: 422280686
Bug: 413162440
Test: treehugger
Change-Id: Ibb8a859538d3bfed8f69861ed97bf47145bfe3a6