Provide Tensor Padding Helpers

[dcvz]

Feature description

Would be great to have helpers in Tensor for padding. Similar to PyTorch's pad and Candle's pad_with_zeros

Additional Information

Some API like this would likely be good (result of conversation on Discord):

pub fn pad<const D: usize>(self, pad: Padding, pad_mode: PadMode, value: K::Elem) -> Tensor<B, D, K>


// Possible definition of padding
pub struct Padding {
    left: usize,
    right: usize,
    top: usize,
    bottom: usize,
}
impl Padding {
    pub fn uniform(value: usize) -> Self {
        Self {
            left: value,
            right: value,
            top: value,
            bottom: value,
        }
    }
    
    // Additional helpers to create useful padding configs
}

[jcmullwh]

Hi, I can take a shot at this one!