Define default value for vars shadowing params (#11307)

* Define default value for vars shadowing params

* Remove from package.json

* Only convert traverse the params if needed

This prevents this plugin from running after the destructuring
transform, which causes #11256

* Review

* Review

* Update packages/babel-plugin-transform-parameters/src/params.js [skip ci]

Co-Authored-By: Brian Ng <bng412@gmail.com>

Co-authored-by: Brian Ng <bng412@gmail.com>

packages/babel-plugin-transform-parameters/test/fixtures/parameters/var-same-as-array-pattern-param/output.js

@@ -1,9 +1,9 @@
 function foo(_ref) {
   var a = _ref.a,
       b = _ref.b;
-  return function () {
+  return function (a) {
     var a = 3;
     var c = 2;
     var d = a + b + c;
-  }();
+  }(a);
 }