[`refurb`] Implement `unnecessary-enumerate` (`FURB148`) (#7454)
## Summary
Implement
[`no-ignored-enumerate-items`](https://github.com/dosisod/refurb/blob/master/refurb/checks/builtin/no_ignored_enumerate.py)
as `unnecessary-enumerate` (`FURB148`).
The auto-fix considers if a `start` argument is passed to the
`enumerate()` function. If only the index is used, then the suggested
fix is to pass the `start` value to the `range()` function. So,
```python
for i, _ in enumerate(xs, 1):
...
```
becomes
```python
for i in range(1, len(xs)):
...
```
If the index is ignored and only the value is ignored, and if a start
value greater than zero is passed to `enumerate()`, the rule doesn't
produce a suggestion. I couldn't find a unanimously accepted best way to
iterate over a collection whilst skipping the first n elements. The rule
still triggers, however.
Related to #1348.
## Test Plan
`cargo test`
---------
Co-authored-by: Dhruv Manilawala <dhruvmanila@gmail.com>
Co-authored-by: Charlie Marsh <charlie.r.marsh@gmail.com>
