Add back compat config for NSD

Add back compat config for RUN_NATIVE_NSD_ONLY_IF_LEGACY_APPS, which was
lost when moving NsdManager to framework-connectivity-t.

This causes NsdManager to start mdnsresponder again when used by apps
with target SDK < 31.

The change also changes the compat ID used, to make sure it does not
conflict with the ID already in use in S and below, when the module is
installed on such a platform. This is the only ChangeId used by
framework-t.

Also add a CtsNetTestCasesMaxTargetSdk30 test to verify that behavior.

Bug: 235355681
Test: atest CtsNetTestCasesMaxTargetSdk30
Change-Id: I7ca6051d0a4ba5aff3e44bece2cbac22eb1be32d
diff --git a/tests/cts/net/Android.bp b/tests/cts/net/Android.bp
index 62f37bb..a6179fc 100644
--- a/tests/cts/net/Android.bp
+++ b/tests/cts/net/Android.bp
@@ -128,3 +128,18 @@
     ],
 }
 
+android_test {
+    name: "CtsNetTestCasesMaxTargetSdk30",  // Must match CtsNetTestCasesMaxTargetSdk30 annotation.
+    defaults: [
+        "CtsNetTestCasesDefaults",
+        "CtsNetTestCasesApiStableDefaults",
+    ],
+    target_sdk_version: "30",
+    package_name: "android.net.cts.maxtargetsdk30",  // CTS package names must be unique.
+    instrumentation_target_package: "android.net.cts.maxtargetsdk30",
+    test_suites: [
+        "cts",
+        "general-tests",
+        "mts-networking",
+    ],
+}