Add methods for managing CAs to DevicePolicyManager(Service)

Guard install/uninstall by enforcing that the caller have the new system-only permission MANAGE_CA_CERTIFICATES.
Also include API methods for asking whether there are any User CA certs
installed, or if one by a particular name is installed in the keystore.

CA certs will be installed via KeyChain into the TrustedCertificateStore.

Bug: 8232670

Change-Id: I17b47a452e72eb4fe556dc6db823a46c6e854be8

keystore/java/android/security/KeyChain.java

@@ -443,7 +443,10 @@ public final class KeyChain {
             }
             @Override public void onServiceDisconnected(ComponentName name) {}
         };
-        boolean isBound = context.bindService(new Intent(IKeyChainService.class.getName()),
+        Intent intent = new Intent(IKeyChainService.class.getName());
+        ComponentName comp = intent.resolveSystemService(context.getPackageManager(), 0);
+        intent.setComponent(comp);
+        boolean isBound = context.bindService(intent,
                                               keyChainServiceConnection,
                                               Context.BIND_AUTO_CREATE);
         if (!isBound) {