VideoBackendBase: Clarify function name

Rename GetDefaultBackendName to GetDefaultBackendConfigName to
distinguish it from the display name.

Source/Android/app/src/main/java/org/dolphinemu/dolphinemu/NativeLibrary.java

@@ -302,7 +302,7 @@ public final class NativeLibrary
 
   public static native int DefaultCPUCore();
 
-  public static native String GetDefaultGraphicsBackendName();
+  public static native String GetDefaultGraphicsBackendConfigName();
 
   public static native int GetMaxLogLevel();
 

Source/Android/app/src/main/java/org/dolphinemu/dolphinemu/features/settings/model/StringSetting.kt

@@ -45,7 +45,7 @@ enum class StringSetting(
         Settings.FILE_DOLPHIN,
         Settings.SECTION_INI_CORE,
         "GFXBackend",
-        NativeLibrary.GetDefaultGraphicsBackendName()
+        NativeLibrary.GetDefaultGraphicsBackendConfigName()
     ),
     MAIN_DUMP_PATH(Settings.FILE_DOLPHIN, Settings.SECTION_INI_GENERAL, "DumpPath", ""),
     MAIN_LOAD_PATH(Settings.FILE_DOLPHIN, Settings.SECTION_INI_GENERAL, "LoadPath", ""),