DO NOT MERGE Add scan background mode to Settings.Global.

This enables us to mess with the different scan intervals and shift
clients to a different scan mode in the background based on what scan
interval values we choose for the different power modes.

Bug: 71765044
Test: None. Just adding a key.
Change-Id: Id48ebc521dd3fe8a68c9c4c0bdb1018ea5b3743e
diff --git a/core/tests/coretests/src/android/provider/SettingsBackupTest.java b/core/tests/coretests/src/android/provider/SettingsBackupTest.java
index cc36b96..63343be 100644
--- a/core/tests/coretests/src/android/provider/SettingsBackupTest.java
+++ b/core/tests/coretests/src/android/provider/SettingsBackupTest.java
@@ -129,6 +129,7 @@
                     Settings.Global.BLE_SCAN_BALANCED_INTERVAL_MS,
                     Settings.Global.BLE_SCAN_LOW_LATENCY_WINDOW_MS,
                     Settings.Global.BLE_SCAN_LOW_LATENCY_INTERVAL_MS,
+                    Settings.Global.BLE_SCAN_BACKGROUND_MODE,
                     Settings.Global.BLUETOOTH_A2DP_SINK_PRIORITY_PREFIX,
                     Settings.Global.BLUETOOTH_A2DP_SRC_PRIORITY_PREFIX,
                     Settings.Global.BLUETOOTH_A2DP_SUPPORTS_OPTIONAL_CODECS_PREFIX,