Migrate Doze flags to DeviceConfig.

This migrates flags inside DeviceIdleController to DeviceConfig.
DeviceConfig is the recommended way and using it means
that we only operate/parse the set of flags that changed instead of
every single flag whenever one of them changes.

Bug: 124466289
Test: atest CtsHostsideNetworkTests
Test: atest FrameworksMockingServicesTests:DeviceIdleControllerTest
Test: atest SettingsProviderTest:SettingsBackupTest
Change-Id: I7fff451b641eee43a13e77df7b40db5b3af16d58
diff --git a/api/module-lib-current.txt b/api/module-lib-current.txt
index 17545a4..8186c9c 100644
--- a/api/module-lib-current.txt
+++ b/api/module-lib-current.txt
@@ -129,6 +129,14 @@
 
 }
 
+package android.provider {
+
+  public final class DeviceConfig {
+    field public static final String NAMESPACE_DEVICE_IDLE = "device_idle";
+  }
+
+}
+
 package android.util {
 
   public class AtomicFile {