Move internal modules to “internal” folder.

.internal/baseGetAllKeys.js

@@ -0,0 +1,19 @@
+import arrayPush from './.internal/arrayPush.js';
+
+/**
+ * The base implementation of `getAllKeys` and `getAllKeysIn` which uses
+ * `keysFunc` and `symbolsFunc` to get the enumerable property names and
+ * symbols of `object`.
+ *
+ * @private
+ * @param {Object} object The object to query.
+ * @param {Function} keysFunc The function to get the keys of `object`.
+ * @param {Function} symbolsFunc The function to get the symbols of `object`.
+ * @returns {Array} Returns the array of property names and symbols.
+ */
+function baseGetAllKeys(object, keysFunc, symbolsFunc) {
+  const result = keysFunc(object);
+  return Array.isArray(object) ? result : arrayPush(result, symbolsFunc(object));
+}
+
+export default baseGetAllKeys;