[mlir][Linalg] Add canonicalization of linalg op -> dim op.

Add canonicalization to replace use of the result of a linalg
operation on tensors in a dim operation, to use one of the operands of
the linalg operations instead. This allows the linalg op itself to be
deleted when all its non-dim uses are removed (say through tiling, etc.)

Differential Revision: https://reviews.llvm.org/D93076