[CS01]Remove hidden API usage of NetworkCapabilities

The connection service will become the mainline module. The mutable
NetworkCapabilities is deprecated, and the NetworkCapabilities should
be built through their Builder instead.

Bug: 170598012
Test: atest FrameworksNetTests
Test: atest IpConnectivityMetricsTest
Change-Id: I73a4d3a7c118b9cef037ed52efb96ed123da2fa5

framework/src/android/net/NetworkCapabilities.java

@@ -2085,9 +2085,10 @@ public final class NetworkCapabilities implements Parcelable {
     /**
      * Check if private dns is broken.
      *
-     * @return {@code true} if {@code mPrivateDnsBroken} is set when private DNS is broken.
+     * @return {@code true} if private DNS is broken on this network.
      * @hide
      */
+    @SystemApi
     public boolean isPrivateDnsBroken() {
         return mPrivateDnsBroken;
     }
@@ -2329,6 +2330,17 @@ public final class NetworkCapabilities implements Parcelable {
             return this;
         }
 
+        /**
+         * Completely clears the contents of this object, removing even the capabilities that are
+         * set by default when the object is constructed.
+         * @return this builder
+         */
+        @NonNull
+        public Builder clearAll() {
+            mCaps.clearAll();
+            return this;
+        }
+
         /**
          * Sets the owner UID.
          *