[mlir][Linalg] Side effects interface for Linalg ops

The LinalgDependenceGraph and alias analysis provide the necessary analysis for the Linalg fusion on buffers case.

However this is not enough for linalg on tensors which require proper memory effects to play nicely with DCE and other transformations.
This revision adds side effects to Linalg ops that were previously missing and has 2 consequences:
1. one example in the copy removal pass now fails since the linalg.generic op has side effects and the pass does not perform alias analysis / distinguish between reads and writes.
2. a few examples in fusion-tensor.mlir need to return the resulting tensor otherwise DCE automatically kicks in as part of greedy pattern application.

Differential Revision: https://reviews.llvm.org/D90762