Launch TetherSettings via Settings.ACTION_TETHER_SETTINGS

Bug: 149068177
Test: Build, Flash, manual test.
Change-Id: If01bdeb7f6ea021cc28c462360a969985882348b

AndroidManifest.xml

@@ -482,6 +482,7 @@
             android:parentActivityName="Settings">
             <intent-filter>
                 <action android:name="android.intent.action.MAIN" />
+                <action android:name="android.settings.TETHER_SETTINGS" />
                 <category android:name="android.intent.category.DEFAULT" />
                 <category android:name="android.intent.category.VOICE_LAUNCH" />
             </intent-filter>