[MLIR][Linalg] Pattern to fold AddOp to accumulation via contraction op's dest (#110514)

Replaces a linalg.add with one operand the single user of a contraction,
which has a zero-filled, "identity-

[MLIR][Linalg] Pattern to fold AddOp to accumulation via contraction op's dest (#110514)

Replaces a linalg.add with one operand the single user of a contraction,
which has a zero-filled, "identity-mapped" destination and is dominated
by the `other` operand, by the contraction with `other` as its dest.

Benefits include elision of an elementwise op, namely the linalg.add,
and removing a tensor.empty as a destination which is likely to require
an allocation upon bufferization.

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