Update on "[compiler] Allow functions containing refs to be returned"

Summary:
We previously were excessively strict about preventing functions that access refs from being returned--doing so is potentially valid for hooks, because the return value may only be used in an event or effect.

[ghstack-poisoned]

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/return-ref-callback.expect.md

@@ -4,6 +4,8 @@
 ```javascript
 // @flow @validateRefAccessDuringRender @validatePreserveExistingMemoizationGuarantees
 
+import {useRef} from 'react';
+
 component Foo() {
   const ref = useRef();
 
@@ -26,6 +28,8 @@ export const FIXTURE_ENTRYPOINT = {
 ```javascript
 import { c as _c } from "react/compiler-runtime";
 
+import { useRef } from "react";
+
 function Foo() {
   const $ = _c(1);
   const ref = useRef();
@@ -48,4 +52,4 @@ export const FIXTURE_ENTRYPOINT = {
 ```
       
 ### Eval output
-(kind: exception) useRef is not defined
+(kind: ok) "[[ function params=0 ]]"

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/return-ref-callback.js

@@ -1,5 +1,7 @@
 // @flow @validateRefAccessDuringRender @validatePreserveExistingMemoizationGuarantees
 
+import {useRef} from 'react';
+
 component Foo() {
   const ref = useRef();