Have a setting in Developer Options to choose bug report handler

- This setting let user determines which app handles the Bug Report
shortcut on device.

BUG:143017534
Test: make -j56 RunSettingsRoboTests
Test: Ensure bug report handler setting shows correct handler apps.
Change-Id: I6160dadcd048e6c79f422e58fcd8defa04f991bb

src/com/android/settings/Settings.java

@@ -169,6 +169,10 @@ public class Settings extends SettingsActivity {
     public static class WifiCallingDisclaimerActivity extends SettingsActivity { /* empty */ }
     public static class MobileNetworkListActivity extends SettingsActivity {}
     public static class GlobalActionsPanelSettingsActivity extends SettingsActivity {}
+    /**
+     * Activity for BugReportHandlerPicker.
+     */
+    public static class BugReportHandlerPickerActivity extends SettingsActivity { /* empty */ }
 
     // Top level categories for new IA
     public static class NetworkDashboardActivity extends SettingsActivity {}