Functions like `function* iterateElements() {}` would not show up in the
editor's navigation outline. With this change, they do.

| **Before** | **After**
|-|-|
|<img width="453" height="280" alt="Screenshot 2025-07-13 at 4 58 22 PM"
src="https://github.com/user-attachments/assets/822f0774-bda2-4855-a6dd-80ba82fffaf3"
/>|<img width="564" height="373" alt="Screenshot 2025-07-13 at 4 58
55 PM"
src="https://github.com/user-attachments/assets/f4f6b84f-cd26-49b7-923b-724860eb18ad"
/>|

Note that I decided to use Zed's agent assistance features to do this PR
as a sort of test run. I don't normally code with an AI assistant, but
figured it might be good in this case since I'm unfamiliar with the
codebase. I must say I was fairly impressed. All the changes in this PR
were done by Claude Sonnet 4, though I have done a manual review to
ensure the changes look sane and tested the changes by running the
re-built `zed` binary with a toy project.

Closes #21631

Release Notes:

- Fixed JS/TS outlines to show generator functions.