🧐[问题] 自定义表单项中如何获取阅读态

### 🧐 问题描述

目前自定义一个表单项，获取不到是否是readonly，手动添加readonly到组件上，但是如何获取到value 的值来分别渲染？
在customInput.tsx中直接获取不到value和readonly，[文档中写自定义表单项遵循](https://ant-design.antgroup.com/components/form-cn#components-form-demo-customized-form-controls)
- 提供受控属性 value 或其它与 [valuePropName](https://ant.design/components/form-cn/#formitem) 的值同名的属性。
- 提供 onChange 事件或 [trigger](https://ant.design/components/form-cn/#formitem) 的值同名的事件。
就算我手动在调用``获取到readonly了，也没法获取到value，使用了Form.useForm，提示`Instance created by `useForm` is not connected to any Form element. Forget to pass `form` prop?`

### 💻 示例代码

index.tsx
```
import {
ProForm,
ProFormText,
ProFormInstance
} from "@ant-design/pro-components";
import { Switch } from "antd";
import React, { useRef, useState } from "react";
import CustomInput from "./CustomInput";

export default function () {
const [readonly, setReadonly] = useState(false);
const formRef = useRef();
function setValue() {
formRef.current?.setFieldsValue({
username: "abc",
customInput: "def"
});
}

return (

```
customInput.tsx
```
import { Input, Form } from "antd";
import { useMemo } from "react";

export default function (props) {
const { value = "", onChange, readonly, ...rest } = props;
console.log("props:", props);
const form = Form.useForm();
const _value = useMemo(() => form[0].getFieldValue(props.name), [value]);

return readonly ? (

```

### 🚑 其他信息

Start by reading the linked customized form controls documentation and the provided index.tsx and customInput.tsx examples, focusing on how ProForm passes readonly and field values to a custom control. Reproduce the behavior with the shown setValue and readonly toggle, then document or implement a supported way for the custom input to render its read-only value.

Written by the indexing model from the issue text.