add optional and tooltip support for form label

Add a `FormLabel` component:

```ts
interface FormLabelProps {
  optional?: string | boolean
  tooltip?: ReactNode
}

<FormLabel optional tooltip="some tooltip">{label}</FormLabel>
```

Also we can use `FormLabel` in `FormTextInput` to simplify the usage:

```ts
interface FormTextInputProps extends FormLabelProps {}

<FormTextInput  optional tooltip="some tooltip" />
```