Move ACTION_CLEAR_DNS_CACHE to ConnectivityManager

- As API review feedback, move ACTION_CLEAR_DNS_CACHE form Intent
  to ConnectivityManager.

- Rename to "android.net.action.CLEAR_DNS_CACHE" because of lint
  suggestion.
frameworks/base/packages/Connectivity/framework/src/android/net/
ConnectivityManager.java:449: error: Inconsistent action value;
expected `android.net.action.CLEAR_DNS_CACHE`, was
`android.intent.action.CLEAR_DNS_CACHE` [ActionValue]

Bug: 183937999
Test: atest FrameworksNetTests
Test: atest ActivityTaskManagerServiceTests
Test: atest android.permission2.cts.PermissionPolicyTest
Test: atest CtsNetTestCases
Change-Id: Iae8aa0ba10dfc7581f0cfaab82643edbee789e2f

framework/src/android/net/ConnectivityManager.java

@@ -449,6 +449,15 @@ public class ConnectivityManager {
     public static final String ACTION_PROMPT_PARTIAL_CONNECTIVITY =
             "android.net.action.PROMPT_PARTIAL_CONNECTIVITY";
 
+    /**
+     * Clear DNS Cache Action: This is broadcast when networks have changed and old
+     * DNS entries should be cleared.
+     * @hide
+     */
+    @SdkConstant(SdkConstantType.BROADCAST_INTENT_ACTION)
+    @SystemApi(client = SystemApi.Client.MODULE_LIBRARIES)
+    public static final String ACTION_CLEAR_DNS_CACHE = "android.net.action.CLEAR_DNS_CACHE";
+
     /**
      * Invalid tethering type.
      * @see #startTethering(int, boolean, OnStartTetheringCallback)