- Reverts `NotificationWorker` from being a `ListenableWorker` back to `Worker`
- Removed all code related to the ListenableWorker implementation of NotificationWorker

- Add a `ReceiveReceiptWorker` to call `sendReceiveReceipt(notificationId)`

- removed OSDelayTaskController.kt since no longer used now that we use Worker with a delay
- removed MockDelayTaskController.java which is used in unit tests
- removed other code related to these two classes

- unit tests fail when ReceiveReceiptWorker runs with a delay so make no delay for unit tests

- a few unit tests related to sending receive receipts  were failing due to "Main looper has queued unexecuted runnables. This might be the cause of the test failure." even after awaiting a long time (flaky pass/fail)

- removed test `testNotificationReceivedNoSendReceivedRequest_Delay` because no longer testing the delay in unit tests and other receive receipt tests are sufficient

- unit tests sending receive receipts were failing when the ReceiveReceiptWorker has constraint of `setRequiredNetworkType(NetworkType.CONNECTED)`

- they were failing even though a check to `NetworkInfo.isConnected()` returns `true`

- so, refactor `buildConstraints` out of the method `beginEnqueueingWork` so it can be shadowed to return no constraints when building the work request for unit tests