Added a Fix to search bar that allows it be unfocused when tapped anywhere outside the search bar.

I have attached below the app flow after implementing the fix.

https://github.com/flutter/flutter/assets/54017876/70915c47-9b77-4a43-a128-8706107f921f

Issue that gets resolved by this fix: #145096

*If you had to change anything in the [flutter/tests] repo, include a link to the migration guide as per the [breaking change policy].*