Test: add tests to testChooseDunUpstreamByAutomaticMode_*

Add dun network test cases as follows.

Overall test coverage:
- testChooseDunUpstreamByAutomaticMode (original):
  common, test#1, test#2
- testChooseDunUpstreamByAutomaticMode_defaultNetworkWifi (new):
  test#3, test#4
- testChooseDunUpstreamByAutomaticMode_loseDefaultNetworkWifi (new):
  test#5
- testChooseDunUpstreamByAutomaticMode_defaultNetworkCell (new):
  test#5, test#7
- testChooseDunUpstreamByAutomaticMode_loseAndRegainDun (new):
  test#8
- testChooseDunUpstreamByAutomaticMode_switchDefaultFromWifiToCell
  (new):
  test#9, test#10

Overall test cases:
+-------+-------+-------+-------+-------+
| Test  | WiFi  | Cellu |  Dun  | Expec |
| Case  |       | alr   |       | ted   |
|   #   |       |       |       | Upstr |
|       |       |       |       | eam   |
+-------+-------+-------+-------+-------+
|   -   |       |       |       |   -   | --+
+-------+-------+-------+-------+-------+   |
|   -   |       |   V   |       |   -   |   |
+-------+-------+-------+-------+-------+   |   Implemented
|   -   |       |   V   |   O   |  Dun  |   +-- in chooseDun
+-------+-------+-------+-------+-------+   |   UpstreamTest
|   -   |   V   |   O   |   O   |  WiFi |   |   Common()
+-------+-------+-------+-------+-------+   |
|   -   |   V   |   O   |       |  WiFi | --+
+-------+-------+-------+-------+-------+
|       |   O   |   V   |       |   -   |
|   1   +-------+-------+-------+-------+
|       |   O   |   V   |   O   |  Dun  |
+-------+-------+-------+-------+-------+
|       |   O   |   V   |       |   -   |
|   2   +-------+-------+-------+-------+
|       |   O   |   V   |   O   |  Dun  |
+-------+-------+-------+-------+-------+
|   3   |   V   |   O   |       |  WiFi | (new)
+-------+-------+-------+-------+-------+
|   4   |   V   |       |       |  WiFi | (new)
+-------+-------+-------+-------+-------+
|   5   |       |       |   O   |  Dun  | (new)
+-------+-------+-------+-------+-------+
|   6   |       |   V   |   O   |  Dun  | (new)
+-------+-------+-------+-------+-------+
|   7   |       |       |   O   |  Dun  | (new)
+-------+-------+-------+-------+-------+
|       |       |       |       |   -   | (new)
|   8   +-------+-------+-------+-------+
|       |       |       |   O   |  Dun  |
+-------+-------+-------+-------+-------+
|       |   V   |       |   O   |  WiFi | (new)
|   9   +-------+-------+-------+-------+
|       |   V   |       |       |  WiFi |
+-------+-------+-------+-------+-------+
|       |   O   |   V   |       |   -   | (new)
|   10  +-------+-------+-------+-------+
|       |   O   |   V   |   O   |  Dun  |
+-------+-------+-------+-------+-------+

Annotation:
1. "V" means that the given network is connected and
   it is default network.
2. "O" means that the given network is connected and
   it is not default network.

Bug: 257408654
Test: atest ConnectivityCoverageTests
Change-Id: Ie7beda1a8fcfd2a3f2600ca601f58d869144d275
1 file changed