Fix ordering for `force-sort-within-sections` (#8665)
Fixes #8661
## Summary
Imports like `from x import y` don't have an "asname" for the module, so
they were placed before imports like `import x as w` since `None` <
`Some(s)` for any string s.
The fix is to first sort by `first_alias`, since it's `None` for `import
x as w`, and then by `asname`.
## Test Plan
I included the example from the issue to avoid future regressions.
