Make ListView friendlier to ? syntax

[grod220]

At the moment, ListView is returning ProgramError everywhere. This makes Pinnochio consumers required to map the error:

pub fn unpack_list_view(data: &[u8]) -> Result<ListViewReadOnly<'_, Bid>, PinocchioErr> {
    assert_discriminator(data)?;
    let (_, slice_region) = data.split_at(ArrayDiscriminator::LENGTH);
    let res = ListView::<Bid>::unpack(slice_region).map_err(|e| u64::from(e).into())?;
    Ok(res)
}

The primary goal of this change is to enable the direct use of the ? operator in consuming code by returning PodSliceError instead and implementing From traits to both program error types. After:

pub fn unpack_list_view(data: &[u8]) -> Result<ListViewReadOnly<'_, Bid>, PinocchioErr> {
    assert_discriminator(data)?;
    let (_, slice_region) = data.split_at(ArrayDiscriminator::LENGTH);
    let res = ListView::<Bid>::unpack(slice_region)?;
    Ok(res)
}

Change type

Breaking change. Several returned err types have changed. Will require major version bump. Open to thoughts on how to handle this or if this is the right change in general.

[buffalojoec]

Based. Gud fix. Just a few small things.

[buffalojoec]

Cool! Thanks for throwing in some extra variants.

[joncinque]

Pinocchio will start using the same program error as the sdk soon, so I would prefer to stick with ProgramError: anza-xyz/pinocchio#112

Edit: mainly because it's a huge hassle to upgrade everything when there's a breaking change to spl-pod, I would avoid it

[grod220]

Oh! If those types are converging, then this is indeed not necessary. Will revert.