Add feature flag as a device_config flag for LPH to search.

Bug: 294858168
Test: manual + unit
Flag: settings_long_press_home_button_to_search
Change-Id: Ib18b672338d9976284d7fdb06590e4239de9ee9c
diff --git a/src/com/android/settings/core/SettingsUIDeviceConfig.java b/src/com/android/settings/core/SettingsUIDeviceConfig.java
index 404b0b4..4d96385 100644
--- a/src/com/android/settings/core/SettingsUIDeviceConfig.java
+++ b/src/com/android/settings/core/SettingsUIDeviceConfig.java
@@ -47,4 +47,9 @@
      */
     public static final String BT_LE_AUDIO_DEVICE_DETAIL_ENABLED =
             "bt_le_audio_device_detail_enabled";
+    /**
+     * {@code true} if long press home button to search is enabled.
+     */
+    public static final String LONG_PRESS_HOME_BUTTON_TO_SEARCH =
+            "long_press_home_button_to_search";
 }