Rename all proposal plugins to -proposal- from -transform- (#6570)

packages/babel-plugin-proposal-function-sent/test/fixtures/function-sent/basic/expected.js

@@ -0,0 +1,13 @@
+let gen = (() => {
+  var _ref = _skipFirstGeneratorNext(function* () {
+    let _functionSent = yield;
+
+    let sent = _functionSent;
+  });
+
+  return function gen() {
+    return _ref.apply(this, arguments);
+  };
+})();
+
+function _skipFirstGeneratorNext(fn) { return function () { var it = fn.apply(this, arguments); it.next(); return it; }; }