Rename plugins to libs and update all file references

libs/vendor/illuminate/contracts/Support/HasOnceHash.php

@@ -0,0 +1,13 @@
+<?php
+
+namespace Illuminate\Contracts\Support;
+
+interface HasOnceHash
+{
+    /**
+     * Compute the hash that should be used to represent the object when given to a function using "once".
+     *
+     * @return string
+     */
+    public function onceHash();
+}