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

packages/babel-plugin-proposal-function-sent/test/fixtures/function-sent/multiple/exec.js

@@ -0,0 +1,23 @@
+const values = [];
+
+function* gen() {
+  values.push(function.sent);
+  values.push(function.sent);
+  values.push(yield "foo");
+  values.push(function.sent);
+  values.push(yield);
+  values.push(function.sent);
+  values.push(function.sent);
+}
+
+const it = gen();
+assert.deepEqual(values, []);
+
+assert.equal(it.next(1).value, "foo");
+assert.deepEqual(values, [ 1, 1 ]);
+
+assert.equal(it.next(2).value, undefined);
+assert.deepEqual(values, [ 1, 1, 2, 2 ]);
+
+assert.equal(it.next(3).done, true);
+assert.deepEqual(values, [ 1, 1, 2, 2, 3, 3, 3 ]);