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

packages/babel-plugin-proposal-function-sent/test/fixtures/generator-kinds/object-method/actual.js

@@ -0,0 +1,5 @@
+const obj = {
+  *gen() {
+    return function.sent;
+  },
+};

packages/babel-plugin-proposal-function-sent/test/fixtures/generator-kinds/object-method/expected.js

@@ -0,0 +1,12 @@
+function _skipFirstGeneratorNext(fn) { return function () { var it = fn.apply(this, arguments); it.next(); return it; }; }
+
+const obj = {
+  gen() {
+    return _skipFirstGeneratorNext(function* () {
+      let _functionSent = yield;
+
+      return _functionSent;
+    })();
+  }
+
+};