This PR fixes an issue where font properties like bolds and italics
would be lost when falling back to a fallback font.

The problem we identified was that when loading the fallback fonts, we
were just loading them by name. This meant that when the original font
had a different font weight (e.g., bold) or style applied to it this
would not cascade to the fallback font.

To reproduce the problem, we used the following text in a Markdown file:

```md
**한글 bold**
```

With the following font configuration in Zed:

```json
"buffer_font_family": "Victor Mono",
"buffer_font_fallbacks": [
  "D2Coding"
]
```

The fonts can be obtained from their respective locations:

- [Victor Mono](https://rubjo.github.io/victor-mono/)
- [D2Coding](https://github.com/naver/d2codingfont)

#### Before

<img width="168" height="46" alt="Screenshot 2026-05-14 at 1 15 15 PM"
src="https://github.com/user-attachments/assets/f6883e4b-8f2b-4285-a110-0e18d562c51d"
/>

#### After

<img width="176" height="53" alt="Screenshot 2026-05-14 at 1 16 04 PM"
src="https://github.com/user-attachments/assets/88d67207-6711-473b-8027-e0acfa58c258"
/>

Closes #51460.

Release Notes:

- macOS: Fixed fallback fonts missing weight/style.

---------

Co-authored-by: Mikayla Maki <mikayla.c.maki@gmail.com>