Fix various issues caused by Vertex/Index buffer conversions (#3762)

* Fix various issues caused by #3679

- The arguments for the 0th dummy vertex buffer were incorrect - it was given an offset of 16 rather than a size of 16.
- The wrong size was used when doing `autoBuffer.Get` on a converted vertex buffer.
- The possibility of a vertex buffer being disposed and then rebound can rebindings to find a different buffer where the current range is out of bounds. Avoid binding when out of range to prevent validation errors.
- The above also affects generation of converted buffers, which was a bit more fatal. Conversion functions now attempt to bound input offset/size.

* Fix offset for converted buffer

Ryujinx.Graphics.Vulkan/IndexBufferState.cs

@@ -49,7 +49,12 @@ namespace Ryujinx.Graphics.Vulkan
             }
             else
             {
-                autoBuffer = gd.BufferManager.GetBuffer(cbs.CommandBuffer, _handle, false, out int _);
+                autoBuffer = gd.BufferManager.GetBuffer(cbs.CommandBuffer, _handle, false, out int bufferSize);
+
+                if (_offset >= bufferSize)
+                {
+                    autoBuffer = null;
+                }
 
                 offset = _offset;
                 size = _size;