Close tab after starting a download when App opens a URL

[mallexxx]

Task/Issue URL: https://app.asana.com/0/1202406491309510/1208315400860384/f

Description:

• Close empty tab created when opening a URL with the app after download has started
• Add URL and Title to the dragging pasteboard when dragging a URL from the Address Bar
• Improve code readability in some places

Steps to test this PR:

1. Drag a download link (e.g. from Asana) to the Tab Bar, validate the new tab is closed
2. Drag a download link onto the "+" in the Tab Bar, validate the new tab is closed
3. Drag a download link onto the "+" button when the Tab Bar is in overflown (scrollable) state, validate the new tab is closed
4. Drag a download link onto the app icon using the app in the Dock), validate the new tab is closed
5. Navigate somewhere; Drag the URL from the Address Bar to Safari bookmark manager, validate a new item is added with title matching the page title

Definition of Done:

• Does this PR satisfy our Definition of Done?

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Internal references:

Pull Request Review Checklist
Software Engineering Expectations
Technical Design Template
Pull Request Documentation

[ayoy]

All worked great (I compared to the release app to get a feeling of how broken things were) and the code looks much better now, thanks @mallexxx!