[App Clips] Add empty state for App Clip

[danielebogo]

📘 Part of: #2549

This PR replaces the Alert with an empty state for when the App Clip can not handle a URL.

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To test

• In Xcode Select the App Clip scheme
• Edit the scheme and the appClipInvocationURLString with https://pca.st/hiddenbrain
• Run the App Clip target
• Confirm you see the placeholder

Checklist

• I have considered if this change warrants user-facing release notes and have added them to CHANGELOG.md if necessary.
• I have considered adding unit tests for my changes.
• I have updated (or requested that someone edit) the spreadsheet to reflect any new or changed analytics.

[dangermattic]

	1 Warning
⚠️	This PR is assigned to the milestone 7.84 ❄️. The due date for this milestone has already passed. Please assign it to a milestone with a later deadline or check whether the release for this milestone has already been finished.

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