Support VirtualEnv and parameterized tests

This commit introduces the use of VirtualEnv to manage test
dependencies. Specifically:
  1. `PythonVirtualenvPreparer` is invoked before running tests
     to set up the isolated Python environment.
  2. The test is declared as a `MoblyBinaryHostTest` to enable
     VirtualEnv compatibility, as `PythonBinaryHostTest` lacks
     this support.
  3. The Mobly test runner is invoked manually to accommodate
     multiple test classes, which is not supported by
     `mobly.test_runner.main()`.
  4. Test classes are refactored to inherit from
     `mobly.BaseTestClass` for compatibility with the Mobly
     test runner.

This change is a prerequisite for subsequent commits that will
install libraries via `pip install`, facilitating isolated
dependency management for improved test reliability and
maintainability.

Also, this commit uses parameterized annotation from absl
to rewrite several tests as paremeterized tests.

Test: atest NetworkStaticLibHostPythonTests
Bug: 335368434
Change-Id: Iffa2f8fa81c3913f3e08cca01b2c009ca959db73
diff --git a/staticlibs/tests/unit/Android.bp b/staticlibs/tests/unit/Android.bp
index e9f8858..3186033 100644
--- a/staticlibs/tests/unit/Android.bp
+++ b/staticlibs/tests/unit/Android.bp
@@ -76,7 +76,14 @@
     test_suites: [
         "general-tests",
     ],
+    // MoblyBinaryHostTest doesn't support unit_test.
     test_options: {
-        unit_test: true,
+        unit_test: false,
+    },
+    // Needed for applying VirtualEnv.
+    version: {
+        py3: {
+            embedded_launcher: false,
+        },
     },
 }