Don't try to visit ArrowFunctionExpression, they cannot be named

They will still be visited if the arrow functions are transformed to regular
functions.

Fixes #5004

packages/babel-plugin-transform-es2015-function-name/test/fixtures/function-name/with-arrow-functions-transform/actual.js

@@ -0,0 +1,3 @@
+const x = () => x;
+const y = x => x();
+const z = { z: () => y(x) }.z;

packages/babel-plugin-transform-es2015-function-name/test/fixtures/function-name/with-arrow-functions-transform/expected.js

@@ -0,0 +1,9 @@
+const x = function x() {
+  return x;
+};
+const y = function y(x) {
+  return x();
+};
+const z = { z: function z() {
+    return y(x);
+  } }.z;

packages/babel-plugin-transform-es2015-function-name/test/fixtures/function-name/with-arrow-functions-transform/options.json

@@ -0,0 +1,3 @@
+{
+  "plugins": ["external-helpers", "transform-es2015-function-name", "transform-es2015-arrow-functions"]
+}