Function execute_spatial_matrix_multiply 

pub fn execute_spatial_matrix_multiply<F: DspFloat>(
    client: &Client,
    input: &Handle,
    weights: &Handle,
    output: &Handle,
    channels: usize,
    samples: usize,
)

output = W · input for a dense row-major W ([channels, channels]) on a [channels, samples] buffer of F: one matrix product (crate::linalg::matmul).