Rename _handlerTag to handlerTag

[jgonet]

Description

Fixes #1354.

We didn't rename all instances of _handlerTag to handlerTag. That caused waitFor tag resolution to fail and this prop was ignored.

Test code

import React, {useRef} from 'react';
import {StyleSheet, View, ScrollView, Text} from 'react-native';
import {
  NativeViewGestureHandler,
  PanGestureHandler,
} from 'react-native-gesture-handler';

const App = () => {
  const panRef = useRef<PanGestureHandler>(null);
  return (
    <View style={styles.container}>
      <PanGestureHandler ref={panRef}>
        <NativeViewGestureHandler waitFor={panRef}>
          <ScrollView style={styles.container}>
            {Array(50)
              .fill(0)
              .map((_, index) => (
                <Text
                  key={`item-${index}`}
                  style={styles.item}>{`item-${index}`}</Text>
              ))}
          </ScrollView>
        </NativeViewGestureHandler>
      </PanGestureHandler>
    </View>
  );
};

const styles = StyleSheet.create({
  container: {
    flex: 1,
  },
  item: {
    padding: 6,
    margin: 3,
    backgroundColor: '#999',
  },
});
export default App;