Move apf test to a standalone file

This is a no-op refactoring, which is preparation for follow-up
changes to add more apfv4 tests.

This includes:
  1. Add a entry point for multi-device tests to collect
     test cases from different files.
  2. Move multi-device initialization code to a base class.
  3. Make different test classes inherit the base class.

Test: m connectivity_multi_devices_snippet && \
      atest CtsConnectivityMultiDevicesTestCases
Bug: 350880989
Change-Id: I294c85d8e09633bbf02ba1543b9f2ea3e988e20d
diff --git a/tests/cts/multidevices/Android.bp b/tests/cts/multidevices/Android.bp
index dc90adb..5f062f1 100644
--- a/tests/cts/multidevices/Android.bp
+++ b/tests/cts/multidevices/Android.bp
@@ -19,9 +19,11 @@
 
 python_test_host {
     name: "CtsConnectivityMultiDevicesTestCases",
-    main: "connectivity_multi_devices_test.py",
+    main: "run_tests.py",
     srcs: [
+        "apfv4_test.py",
         "connectivity_multi_devices_test.py",
+        "run_tests.py",
     ],
     libs: [
         "mobly",