Review reminders: allow scheduling exact alarms

```
* A user can request [android.Manifest.permission.SCHEDULE_EXACT_ALARM] on API 31+
* which allows scheduling of exact alarms.
*
* TODO: We do not currently support this in the manifest, but we should do
* before launch
https://developer.android.com/about/versions/14/changes/schedule-exact-alarms
```

Originally suggested by David. We should investigate whether it's ok to give AnkiDroid the exact alarm permission: will it ring any alarm bells on the Google Play store etc.?

This would indeed be a nice feature to have. I'm envisioning having it off by default, but if the user enters the troubleshooting screen and decides to grant the permission, we should utilize it.