Stop using IntentService and use async receiver (2/2 - contract)

Also:
- Set FLAG_RECEIVER_INCLUDE_BACKGROUND for ACTION_EVENT_REMINDER
- Remove the wake lock; with goAsync() now it's not needed.

Test: Manual test with: adb shell am broadcast --receiver-include-background -a android.intent.action.EVENT_REMINDER -d content:
Bug 35207106

Change-Id: I9e456f473f13b71df6e0dd1a1abdb0df8c26e6c7