Defer LOCKED_BOOT_COMPLETED and BOOT_COMPLETED broadcasts.

Until the first time any process in the UID is started.

This feature is enabled by device_config flag "defer_boot_completed_broadcast" which has possible value:
0 defer none.
1 defer LOCKED_BOOT_COMPLETED and BOOT_COMPLETED broadcasts of all apps.
2 defer UID that is background restricted.
4 defer UID that has targetSdkVersion T+.
Except value -1 and 1, other values can be bit-OR-ed to combine multiple
conditions.

The default is to defer apps that are both background restricted AND targetSdkVersion T+.

Bug: 203704822
Test: atest services/tests/servicestests/src/com/android/server/am/BroadcastRecordTest#testDeferBootCompletedBroadcast and #testDeferBootCompletedBroadcast_dispatcher
Change-Id: Ia48ca3704a2f371e8bbe4d93df90652191dc2f99