Add permanent iOS survey

[samsymons]

Task: https://app.asana.com/0/1207619243206445/1208454188907378/f

This PR adds the permanent iOS survey. This PR is very similar to previous surveys such as #95, except this survey adds a targetPercentile of 0.3.

Testing instructions:

Note: This survey has a 30% chance of appearing. If it doesn't appear, you could delete and reinstall the app to get a new percentile roll, or you may hardcode RemoteMessagingPercentileUserDefaultsStore to give you a valid value.

1. Update RemoteMessageRequest to include the sample URL attached in the comments below
2. Update shouldProcessConfig to always return true
3. Now we need to test that the install date range is working. We have no method in the Debug menu for overriding this so for now you'll need to use a local copy of BSK and search for the line case let matchingAttribute as DaysSinceInstalledMatchingAttribute
4. Underneath the line mentioned above, you can override daysSinceInstall value to check the range. Try it with 0, 5, and 10, and check that the message only appears for the 5 case
5. Finally, set the value back to one that matches the range, and check that opening the link correctly opens the survey

[github-actions]

Your PR is hosted at https://staticcdn.duckduckgo.com/remotemessaging/config/staging/pre/ios-config.json

[amddg44]

LGTM! Happy to take another pass if you’d like if the parameters change, but all the logic worked as expected & the survey URL built correctly 🙂