Add OutVariableArgumentProvider for 'out' parameters

[sharwell]

Statistics for Compilers.sln before this change:

Solution:
  Total:     4307883
  Correct:   391422
  Incorrect: 3916461
  Missing:   0

After this change:

Solution:
  Total:     4307883
  Correct:   399915 (+8493)
  Incorrect: 3907968 (-8493)
  Missing:   0

[azure-pipelines]

Azure Pipelines successfully started running 4 pipeline(s).

[JoeRobich]

Is the filtering above guaranteed to limit us to a single result? or would an exception here mean the test should be rewritten to remove ambiguity?

[sharwell]

It's still possible to construct a test that the framework doesn't support. We'd have to modify it at that time to support the specifics of the new test.