editor: extend diff hunk range for custom transform blocks. (#4012)

Reported by Mikayla:

![image](https://github.com/zed-industries/zed/assets/24362066/b744d82e-328f-4554-becf-96f9fa92bfc8)
Note how the line with rust analyzer error does not have a git diff
hunk.
vs:

![image](https://github.com/zed-industries/zed/assets/24362066/e285af7a-b8ab-40e9-a9c6-b4ab8d6c4cd0)

Release Notes:
- N/A
0db7559e96Piotr Osiewicz committed on 1/11/2024, 11:26:12 AM· committed by GitHubparent31689c0
1 file changedLine totals unavailable