wg: Break out crossport dependency

Replace all crossport uses with upstream design
support library components.

Signed-off-by: Harsh Shandilya <me@msfjarvis.dev>

app/src/main/java/com/wireguard/android/util/ClipboardUtils.java

@@ -3,11 +3,10 @@ package com.wireguard.android.util;
 import android.content.ClipData;
 import android.content.ClipboardManager;
 import android.content.Context;
+import android.support.design.widget.Snackbar;
 import android.view.View;
 import android.widget.TextView;
 
-import com.commonsware.cwac.crossport.design.widget.Snackbar;
-
 /**
  * Standalone utilities for interacting with the system clipboard.
  */