Product Form: Fix issue showing share sheet from the bar button item on iPad

[itsmeichigo]

Part of #9788

Description

Previously, we were showing the share sheet from view controller view as the source view. On iPad, when the source view is too large, there is not enough space for the popover to be displayed. Hence when testing the share feature on iPad, the share sheet is not displayed when tapping on the Share button of the product form.

This PR fixes the issue by setting the bar button items in the product form as the source view for the share popover.

Testing instructions

• Build and run the app on an iPad.
• Log in to a store and switch to Products tab.
• Select a product on the list and tap the Share button or tap Share in the ellipsis button.
• Notice that the share popover is displayed correctly.

Screenshots

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• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[wpmobilebot]

You can test the changes from this Pull Request by:

• Clicking here or scanning the QR code below to access App Center
• Then installing the build number pr9797-7d41c7f on your iPhone

If you need access to App Center, please ask a maintainer to add you.

[selanthiraiyan]

🚀