Fixes ZED-1NX

This panic could occur when an `bulk_staging` was set to `Some(...)` and
`sort_by_path` was set to `true`.
When setting `sort_by_path: true`, we call `update_visible_entries(...)`
which then checks if `bulk_staging ` is `Some(...)` and calls
`entry_by_path`. That function accesses `entries`, which still consists
of both headers and entries. But the code
(`entry.status_entry().unwrap()`) assumes that there are no headers in
the entry list if `sort_by_path: true`.

```rust
if GitPanelSettings::get_global(cx).sort_by_path {
    return self
        .entries
        .binary_search_by(|entry| entry.status_entry().unwrap().repo_path.cmp(path)) //This unwrap() would panic
        .ok();
}
```

This has now been fixed by clearing all the entries when `sort_by_path`
changes, as this is the only case where our assumptions are invalid. I
also added a test which 1) actually tests the sort_by_path logic 2)
ensures that we do not re-introduce this panic in the future.


Release Notes:

- Fixed a panic that could occur when using `sort_by_path: true` in the
git panel