fix: #2502 Expose set_menu from tao through the TrayHandle struct

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What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature (fixes Expose set_menu from tao through the TrayHandle struct #2502)
• Docs
• New Binding Issue #___
• Code style update
• Refactor
• Build-related changes
• Other, please describe:

Does this PR introduce a breaking change? (check one)

• Yes. Issue #___
• No

The PR fulfills these requirements:

• When resolving a specific issue, it's referenced in the PR's title (e.g. fix: #xxx[,#xxx], where "xxx" is the issue number)
• A change file is added if any packages will require a version bump due to this PR per the instructions in the readme.

If adding a new feature, the PR's description includes:

• A convincing reason for adding this feature (to avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it)

Other information:

Some time ago we added set_menu for system trays: tauri-apps/tao#106
This API is not available via Tauri, and only set_icon is to be found inside app.tray_handle().

This PR exposes set_menu via the TrayHandle struct.

Disclaimer:

I'm not sure if this builds and runs correctly. I'm providing this as a draft PR and I'll be working on it based on feedback.

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Closing in favor of #2532 which is based on next.