intensity_limits would be a better name for dtype_limits

[lagru]

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:

@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.

[lagru]

... or would this function cease being useful because we would stop using intensity conventions for images alltogether?