Updated the results formatter to eliminate redundant data.

The testsuite's results formatter maintains a result_status_counts
structure solely for the purpose of setting the return status code
after the testsuite has run.  This data is redundant with the
result_events structure that contains the results of individual
tests.

There are subtle bugs arising from this redundancy that make some
builds report no errors but a nonzero status.  Rather than try to
make sure these two are always in agreement, I've just rewritten
the code that used to use the counts to now use the per-test
results.

<rdar://problem/30496966>

llvm-svn: 295522