[Catalyst] Network and Intenet screen migration

- Add a flag for the migration
- Add the skeleton of the screen

Test: atest NetworkDashboardScreenTest
Bug: 368355361
Flag: com.android.settings.flags.catalyst_network_provider_and_internet_screen
Change-Id: I37622d318f2a52a7c60c9fa965b94fd135ce0b60

aconfig/catalyst/network_and_internet.aconfig

@@ -0,0 +1,9 @@
+package: "com.android.settings.flags"
+container: "system"
+
+flag {
+  name: "catalyst_network_provider_and_internet_screen"
+  namespace: "android_settings"
+  description: "Flag for Network & Internet"
+  bug: "323791114"
+}