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/Tethering/apex/Android.bp b/Tethering/apex/Android.bp
index a7028b7..60b4e91 100644
--- a/Tethering/apex/Android.bp
+++ b/Tethering/apex/Android.bp
@@ -108,7 +108,10 @@
 
     androidManifest: "AndroidManifest.xml",
 
-    compat_configs: ["connectivity-platform-compat-config"],
+    compat_configs: [
+        "connectivity-platform-compat-config",
+        "connectivity-t-platform-compat-config",
+    ],
 }
 
 apex_key {