Hook up AOD knobs to Settings.Global

This cl creates AlwaysOnDisplayPolicy, which get values for the
following knobs(go/aod-experiments) from Settings.Global:
1. screen_brightness_array
2. dimming_scrim_array
3. prox_screen_off_delay
4. prox_cooldown_trigger
5. prox_cooldown_period

Also update code to make sure AlwaysOnDisplayPolicy is used
everywhere.

Bug: 64899561
Test: runtest -x AlwaysOnDisplayPolicyTest

Change-Id: I2e83ff980771e67177e4964bd83aa68b2bdca65f
diff --git a/core/tests/coretests/src/android/provider/SettingsBackupTest.java b/core/tests/coretests/src/android/provider/SettingsBackupTest.java
index e292c9d..30f7c73 100644
--- a/core/tests/coretests/src/android/provider/SettingsBackupTest.java
+++ b/core/tests/coretests/src/android/provider/SettingsBackupTest.java
@@ -99,6 +99,7 @@
                     Settings.Global.ALARM_MANAGER_CONSTANTS,
                     Settings.Global.ALLOW_USER_SWITCHING_WHEN_SYSTEM_USER_LOCKED,
                     Settings.Global.ALWAYS_FINISH_ACTIVITIES,
+                    Settings.Global.ALWAYS_ON_DISPLAY_CONSTANTS,
                     Settings.Global.ANIMATOR_DURATION_SCALE,
                     Settings.Global.ANOMALY_DETECTION_CONSTANTS,
                     Settings.Global.APN_DB_UPDATE_CONTENT_URL,