fix: use button property for data-tauri-drag-region mouse button detection, closes #7694

[pewsheen]

What kind of change does this PR introduce?

• Bugfix
• Feature
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• New Binding issue #___
• Code style update
• Refactor
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Does this PR introduce a breaking change?

• Yes, and the changes were approved in issue #____
• No

Checklist

• When resolving issues, they are referenced in the PR's title (e.g fix: remove a typo, closes #___, #___)
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Other information

#7694

Updated the data-tauri-drag-region attribute to use the button property instead of the buttons property to check if the left mouse button was pressed.

This change is intended to fix an issue that if the "Tap to Click" option is enabled on the macOS, event.buttons will return 0 and 1 randomly when tapping the element.

Behavior changed
Before this patch, the drag event will be triggered only when the left mouse button is pressed. In this patch, if multiple mouse buttons are clicked along with the left mouse button simultaneously, it would see as the left mouse button clicked and trigger the drag event.

[amrbashir]

I wouldn't consider this a breaking change but just to make sure, I will cc @lucasfernog