Add setFirewallChainEnabled API

To deprecated firewallEnableChildChain netd binder and move the
functionality to tethering (connectivity) mainline module, expose
setFirewallChainEnabled to support the caller outside the module.
Currently the API are still call to netd. Will replace with the
implementation inside tethering (connectivity) module.

Bug: 209935649
Test: atest CtsHostsideNetworkTests
Change-Id: I9b64c9d12260521489a87fbeae5afbee2a8ea8f6
diff --git a/framework/src/android/net/IConnectivityManager.aidl b/framework/src/android/net/IConnectivityManager.aidl
index 6f60a68..f5968a6 100644
--- a/framework/src/android/net/IConnectivityManager.aidl
+++ b/framework/src/android/net/IConnectivityManager.aidl
@@ -236,4 +236,6 @@
     void updateMeteredNetworkDenyList(int uid, boolean add);
 
     void updateFirewallRule(int chain, int uid, boolean allow);
+
+    void setFirewallChainEnabled(int chain, boolean enable);
 }