edit prediction: Fix crash in `highlight_text` (#23766)

This fixes the panics we we're seeing in `EditPreview::highlight_edits`.
The reason for this was that we were interpolating edits incorrectly.

Here's an example:

```rust
let a = 0; // existing code
let c = 2; // suggested by edit prediction
```
The edits would look like this: `[(Point(1, 0)..Point(1, 0), "let c =
2;"]`

Now i type:
```rust
let a = 0; // existing code
let b = 1; // added this line
let c = 2; // suggested by edit prediction
```

Before this change, the `interpolate` function would allow insertions
before the edit prediction edits, the anchors will move to the next
line.
The edits would look now like this: `[(Point(2, 0)..Point(2, 0), "let c
= 2;"]`

However, now we end up with a call to `EditPreview::highlight_edits`,
with the following parameters:
- current_snapshot: 
  ```rust
  let a = 0;
  let b = 1;
  ```
- edits: `[(Point(2, 0)..Point(2, 0), "let c = 2;"]`
- applied_edits_snapshot:
  ```rust
  let a = 0;
  let c = 2;
  ```

And here you can see the issue, applying the `edits` to the
`current_snapshot` should always end up re-creating the text that is
present in the `applied_edits_snapshot`. That is not the case here
though, meaning that the offsets in the new buffer are not correct,
which can either lead to a confusing popup or a crash if the suggestion
is at the end of the file.

Here's a real world example (edit prediction is ONLY suggesting to
delete a new line):

<img width="487" alt="Screenshot 2025-01-27 at 13 05 26"
src="https://github.com/user-attachments/assets/a0a8064e-8cfa-48b2-9f1c-efc2d0d9d7d4"
/>

We fixed this by only allowing interpolation if the user is editing
after all the edit predictions OR if the user edit is a subset of the
model suggestion.



Co-Authored-by: Antonio <antonio@zed.dev>

Release Notes:

- N/A

Co-authored-by: Antonio <antonio@zed.dev>