text: Title: `intensity_limits` would be a better name for `dtype_limits`
  Body: At a first glance I thought, `dtype_limits(...)` would give me the largest and lowest representable number of the dtype of a given image (like `np.finfo()` only for integers and floats). Though, the function actually returns our intensity conventions for a given dtype. So I propose to refactor the function:
  
  ```python
  @deprecate_function(...)
  def dtype_limits(image, clip_negative=False):
      ...
  
  # to
  
  def intensity_limits(dtype, *, clip_negative=False):
      ...
  ```
  
  I'm guessing that this function isn't used too much in our user base and the new name should make the functions purpose a lot clearer. I don't think this refactor needs to be a high priority but I'd like to eventually get to it. At the very latest for skimage2.