Implement share test result reminder for RAT tests (#2977)

...pp/coronatest/notification/ShareTestResultNotification.kt

...natest/notification/ShareTestResultNotificationService.kt

...pp/src/main/java/de/rki/coronawarnapp/main/CWASettings.kt

...de/rki/coronawarnapp/notification/GeneralNotifications.kt

...e/rki/coronawarnapp/notification/NotificationConstants.kt

...de/rki/coronawarnapp/notification/NotificationReceiver.kt

...va/de/rki/coronawarnapp/submission/task/SubmissionTask.kt

...util/encryptionmigration/EncryptedPreferencesMigration.kt

...st/notification/ShareTestResultNotificationServiceTest.kt

...e/rki/coronawarnapp/submission/task/SubmissionTaskTest.kt

.../encryptionmigration/EncryptedPreferencesMigrationTest.kt