rust-index: slicechunktodensity returns Rust result
Ready for removal of the scaffolding.
This time, we allow ourselves a minor optimization: we avoid
allocating for each chunk. Instead, we reuse the same vector,
and perform at most one allocation per chunk.
The `PyList` constructor will copy the buffer anyway.
edition = "2018"
max_width = 79
wrap_comments = true
error_on_line_overflow = true