Updated MPC unit tests to use function abstractions. Most of these updates are made to the C frontend and MPC lowering pass. Additional optimization and ILP solving passes need to be updated.
The assignment and cost model passes now need to factor in Array and Tuple semantics. This requires changes to the CostModel assignments. This also requires the the def-use-graph implementation for constant-index propagation.
Work-around:
- disabled HyCC benchmark tests
- disabled tests that use Op::Select / Op::Store
