Pipe Linalg to LLVM via mlir-cpu-runner

    This CL adds support for functions in the Linalg dialect to run with mlir-cpu-runner.
    For this purpose, this CL adds BufferAllocOp, BufferDeallocOp, LoadOp and StoreOp to the Linalg dialect as well as their lowering to LLVM. To avoid collisions with mlir::LoadOp/StoreOp (which should really become mlir::affine::LoadOp/StoreOp), the mlir::linalg namespace is added.

    The execution uses a dummy linalg_dot function that just returns for now. In the future a proper library call will be used.

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PiperOrigin-RevId: 247476061