Changing HField geometry at runtime - visualization not working

I'd like to change the geometry of a HField at runtime. I am using the following code:
```python
hfield = physics.bind(self._hfield_chunks[geom_idx])
res = hfield.nrow

# Generate terrain in a 2D numpy array bounded to [0, 1]...

start_idx = hfield.adr
physics.model.hfield_data[start_idx:start_idx + res**2] = terrain.ravel()

with physics.contexts.gl.make_current() as ctx:
ctx.call(mjlib.mjr_uploadHField,
physics.model.ptr,
physics.contexts.mujoco.ptr,
hfield.element_id)
```
Unfortunately, while the physics model seems to change as expected, the visualization is not updating to match. In case it's relevant, I'm using dm_control and the above code is called by the `after_step()` callback.

首先跟踪 issue 中所示的 after_step() 回调和 mjr_uploadHField 调用，然后检查 hfield_data 发生变化后 dm_control 如何更新 MuJoCo 可视化状态。当运行时地形变化同时反映在可视化和物理模型中时，即视为完成。

由索引模型根据 Issue 内容生成。