[fix] TextInput calls onFocus if autoFocus={true}

The host node ref is not a dependency of the focus handling. Previously, the
focus callback was not called if the element was auto-focused, because  React
DOM calls `onFocus` while the object ref is `null`.

Fix #2045

packages/examples/pages/text-input/index.js

@@ -14,6 +14,13 @@ export default function TextInputPage() {
   return (
     <Example title="TextInput">
       <View style={styles.container}>
+        <TextInput
+          autoFocus
+          onFocus={() => {
+            console.log('focused');
+          }}
+          style={styles.textinput}
+        />
         <TextInput
           blurOnSubmit={true}
           onSubmitEditing={() => focusNextField()}