## Summary
Closes#1567.
Add both `length-sort` and `length-sort-straight` settings for isort.
Here are a few notable points:
- The length is determined using the
[`unicode_width`](https://crates.io/crates/unicode-width) crate, i.e. we
are talking about displayed length (this is explicitly mentioned in the
description of the setting)
- The dots are taken into account in the length to be compatible with
the original isort
- I had to reorder a few fields of the module key struct for it all to
make sense (notably the `force_to_top` field is now the first one)
## Test Plan
I added tests for the following cases:
- Basic tests for length-sort with ASCII characters only
- Tests with non-ASCII characters
- Tests with relative imports
- Tests for length-sort-straight