[mlir][linalg] Retire PoolingMaxOp/PoolingMinOp/PoolingSumOp.

The pooling ops are among the last remaining hard coded Linalg operations that have no region attached. They got obsolete due to the OpDSL pooling operations. Removing them allows us to delete specialized code and tests that are not needed for the OpDSL counterparts that rely on the standard code paths.

Reviewed By: nicolasvasilache

Differential Revision: https://reviews.llvm.org/D110909