Not a good practice to access AudioQueueBuffer.AudioData by Marshal.ReadIntPtr

I am working on iOS audio. After struggling with IntPtr-s, which might be a AudioQueueBuffer*,
or pointing to raw samples, I finally managed to make things work.

But, I find below code seems not a good practice.

https://github.com/xamarin/xamarin-macios/blob/e45c3ba794e25c4ecb1c076678b733746ca184e4/src/AudioToolbox/AudioQueue.cs#L499

### Steps to Reproduce

Check the source code of AudioQueue.FillAudioData(...).

```c#
public static void FillAudioData (IntPtr audioQueueBuffer, int offset, IntPtr source, int sourceOffset, nint size)
{
// Here, location of field AudioData is almost *hard-coded*
IntPtr target = Marshal.ReadIntPtr (audioQueueBuffer, IntPtr.Size);
unsafe {
byte *targetp = (byte *) target;
byte *sourcep = (byte *) source;
Runtime.memcpy (targetp + offset, sourcep + sourceOffset, size);
}
}
```
### Expected Behavior

1. Use AudioQueueBuffer.AudioData;
2. Use AudioQueueBuffer.CopyToAudioData(IntPtr source, int size).

### Actual Behavior

The implementation seems not a good one.

### Environment

N/A

### Build Logs

N/A

### Example Project (If Possible)

N/A