Update Rust crate optfield to 0.4.0 (#32890)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [optfield](https://redirect.github.com/roignpar/optfield) | workspace.dependencies | minor | `0.3.0` -> `0.4.0` |

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### Release Notes

<details>
<summary>roignpar/optfield (optfield)</summary>

### [`v0.4.0`](https://redirect.github.com/roignpar/optfield/blob/HEAD/CHANGELOG.md#040)

[Compare Source](https://redirect.github.com/roignpar/optfield/compare/v0.3.0...v0.4.0)

-   fix `from` and `merge_fn` when using `cfg` attrs on the original struct fields
-   upgrade dependencies, bumping minimum supported rustc version to 1.61 (required by latest `syn`)

</details>

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This PR has been generated by [Renovate Bot](https://redirect.github.com/renovatebot/renovate).

GitOrigin-RevId: 7377d0cf2df65e2698f2b0e412572a48f4e6fdba

Author: convex-renovate-runner[bot]