Migrate ChooseAccountActivity to DashboardFragment

- Build a controller to generate/manage a list of preferences.
- Move some logics to the controller and add tests.
- Rename to ChooseAccountFragment.

Bug: 73899467
Test: make RunSettingsRoboTests -j
      atest UniquePreferenceTest SettingsGatewayTest
Change-Id: Id2906c4b922ef159d08c803b976671264c54665f
diff --git a/AndroidManifest.xml b/AndroidManifest.xml
index 69416a7..5a0f181 100644
--- a/AndroidManifest.xml
+++ b/AndroidManifest.xml
@@ -2341,7 +2341,7 @@
             android:label="@string/header_add_an_account"
             android:configChanges="orientation|keyboardHidden|screenSize">
             <meta-data android:name="com.android.settings.FRAGMENT_CLASS"
-                       android:value="com.android.settings.accounts.ChooseAccountActivity" />
+                       android:value="com.android.settings.accounts.ChooseAccountFragment" />
         </activity>
 
         <activity android:name=".CryptKeeper"