Migrate UsageStats to Spa

The UsageStats page is for testing only, cannot entry through Settings
Home, but is accessible by enter *#*#4636#*#* in dialer.

Migrate UsageStats to Spa for both improving the UI & performance.

Fix: 244675756
Bug: 235727273
Test: Manual with Settings App
Change-Id: I6ec6e233075a3f79ac1231aecafabf2a71dac716

src/com/android/settings/spa/SpaActivity.kt

@@ -23,9 +23,9 @@ import com.android.settingslib.spa.framework.BrowseActivity
 class SpaActivity : BrowseActivity(SpaEnvironment.settingsPageProviders) {
     companion object {
         @JvmStatic
-        fun startSpaActivity(context: Context, startDestination: String) {
+        fun startSpaActivity(context: Context, destination: String) {
             val intent = Intent(context, SpaActivity::class.java).apply {
-                putExtra(KEY_DESTINATION, startDestination)
+                putExtra(KEY_DESTINATION, destination)
             }
             context.startActivity(intent)
         }