Unregister from oldGestureHandler when component unmounts (#3374)

## Description

We might have discovered a memory leak associated with oldGestureHandler registry. Nothing ever gets removed from it. We noticed a lot of hanging GenericTouchable components at runtime associated with this registry.

## Test plan

<details>
<summary>Tested on the following code:</summary>

```jsx
import { useState } from 'react';
import { Button, View } from 'react-native';
import {
  GestureHandlerRootView,
  PanGestureHandler,
} from 'react-native-gesture-handler';

export default function App() {
  const [show, setShow] = useState(false);

  return (
    <GestureHandlerRootView
      style={{ flex: 1, alignItems: 'center', justifyContent: 'space-around' }}>
      <Button onPress={() => setShow((prev) => !prev)} title="Click me!" />

      {show && (
        <PanGestureHandler>
          <View style={{ width: 100, height: 100, backgroundColor: 'red' }} />
        </PanGestureHandler>
      )}
    </GestureHandlerRootView>
  );
}
```

</details>

with 

```jsx
setInterval(() => console.log(oldHandlers), 1000);
```

added in `handlersRegistry.tsx`

Author: gavrix

src/handlers/createHandler.tsx

@@ -8,7 +8,11 @@ import {
 import { customDirectEventTypes } from './customDirectEventTypes';
 import RNGestureHandlerModule from '../RNGestureHandlerModule';
 import { State } from '../State';
-import { handlerIDToTag, registerOldGestureHandler } from './handlersRegistry';
+import {
+  handlerIDToTag,
+  registerOldGestureHandler,
+  unregisterOldGestureHandler,
+} from './handlersRegistry';
 import { getNextHandlerTag } from './getNextHandlerTag';
 
 import {
@@ -255,6 +259,9 @@ export default function createHandler<
     componentWillUnmount() {
       this.inspectorToggleListener?.remove();
       this.isMountedRef.current = false;
+      if (Platform.OS !== 'web') {
+        unregisterOldGestureHandler(this.handlerTag);
+      }
       RNGestureHandlerModule.dropGestureHandler(this.handlerTag);
       scheduleFlushOperations();
       // We can't use this.props.id directly due to TS generic type narrowing bug, see https://github.com/microsoft/TypeScript/issues/13995 for more context

src/handlers/handlersRegistry.ts

@@ -25,6 +25,10 @@ export function registerOldGestureHandler(
   oldHandlers.set(handlerTag, handler);
 }
 
+export function unregisterOldGestureHandler(handlerTag: number) {
+  oldHandlers.delete(handlerTag);
+}
+
 export function unregisterHandler(handlerTag: number, testID?: string) {
   gestures.delete(handlerTag);
   if (isTestEnv() && testID) {