Rename plugins to libs and update all file references

libs/stripe-php/lib/Exception/ExceptionInterface.php

@@ -0,0 +1,18 @@
+<?php
+
+namespace Stripe\Exception;
+
+// TODO: remove this check once we drop support for PHP 5
+if (\interface_exists(\Throwable::class, false)) {
+    /**
+     * The base interface for all Stripe exceptions.
+     */
+    interface ExceptionInterface extends \Throwable {}
+} else {
+    /**
+     * The base interface for all Stripe exceptions.
+     */
+    // phpcs:disable PSR1.Classes.ClassDeclaration.MultipleClasses
+    interface ExceptionInterface {}
+    // phpcs:enable
+}