Add auto battery saver suggestion notification/dialog

Spec: go/ebs-low-battery-mode-flow

- Basically when the user manually enables battery saver 4 times,
we show this notification to suggest turning on "scheduled"
(i.e. auto) battery saver.

- We show it through 8th time. If the user hits "no thanks",
or if auto-saver is enabled already, we will not show it.

- Introduced a new notification channel "HINTS" with
IMPORTANCE_DEFAULT.

Bug: 74120126
Test: Manual test with ll development/scripts/battery_simulator.py

Change-Id: I713abc59dc7caee6882ba848c3e3aabaf778c2bd
diff --git a/core/tests/coretests/src/android/provider/SettingsBackupTest.java b/core/tests/coretests/src/android/provider/SettingsBackupTest.java
index a504ab9..0d6b24a 100644
--- a/core/tests/coretests/src/android/provider/SettingsBackupTest.java
+++ b/core/tests/coretests/src/android/provider/SettingsBackupTest.java
@@ -585,7 +585,8 @@
                  Settings.Secure.PARENTAL_CONTROL_REDIRECT_URL,
                  Settings.Secure.BLUETOOTH_ON_WHILE_DRIVING,
                  Settings.Secure.LOW_POWER_MANUAL_ACTIVATION_COUNT,
-                 Settings.Secure.LOW_POWER_WARNING_ACKNOWLEDGED);
+                 Settings.Secure.LOW_POWER_WARNING_ACKNOWLEDGED,
+                 Settings.Secure.SUPPRESS_AUTO_BATTERY_SAVER_SUGGESTION);
 
     @Test
     public void systemSettingsBackedUpOrBlacklisted() {