Implement push notifications deleting

[SleepySquash]

Synopsis

Push notifications can be received from the FCM, however they can be replaced but cannot be deleted.

Solution

This PR allows the notifications to be deleted when empty notification body is being sent.

Checklist

• Created PR:
  • In draft mode
  • Name contains issue reference
  • Has type and k:: labels applied
• Before review:
  • Documentation is updated (if required)
  • Tests are updated (if required)
  • Changes conform code style
  • CHANGELOG entry is added (if required)
  • FCM (final commit message) is posted or updated
  • Draft mode is removed
• Review is completed and changes are approved
  • FCM (final commit message) is approved
• Before merge:
  • Milestone is set
  • PR's name and description are correct and up-to-date
  • All temporary labels are removed

[SleepySquash]

FCM

Send `Query.chatItems` to mark `ChatItem`s as delivered when receiving push notifications (#1038)

- impl and use Notification Service Extension on iOS to send `Query.chatItems` query
- refactor `handlePushNotification` to send `Query.chatItems` when receiving push notification on Android
- refactor native `connect()` for `drift` to use `IosUtils.getSharedDirectory()` for iOS
- refactor `NotificationService` to send `Query.chatItems` when receiving foreground notifications

Additionally:
- bootstrap `AndroidUtils.cancelNotification()` for canceling displayed notifications on Android
- bootstrap `IosUtils.cancelNotification()` for canceling displayed notifications on iOS
- refactor Firebase Service Worker on web to support displayed notifications canceling