move all plugin tests out of babel-core and into their appropriate folders

packages/babel-plugin-transform-es2015-function-name/test/fixtures/function-name/class-method/actual.js

@@ -0,0 +1,5 @@
+class Foo {
+  t(t) {
+    return t;
+  }
+}

packages/babel-plugin-transform-es2015-function-name/test/fixtures/function-name/class-method/expected.js

@@ -0,0 +1,13 @@
+let Foo = (function () {
+  function Foo() {
+    babelHelpers.classCallCheck(this, Foo);
+  }
+
+  babelHelpers.createClass(Foo, [{
+    key: "t",
+    value: function t(_t) {
+      return _t;
+    }
+  }]);
+  return Foo;
+})();