Refactor dtype sets in imgaug.py to match migration guide from numpy

[kapiw04]

citing migration guide for numpy2.0 instead of np.sctypes you should Access dtypes explicitly instead.. To maintain the functionality I did the following:

In [1]: import numpy as np
np
In [2]: np.__version__
Out[2]: '1.22.0'

In [3]: np.sctypes
Out[3]:
{'int': [numpy.int8, numpy.int16, numpy.int32, numpy.int64],
 'uint': [numpy.uint8, numpy.uint16, numpy.uint32, numpy.uint64],
 'float': [numpy.float16, numpy.float32, numpy.float64, numpy.float128],
 'complex': [numpy.complex64, numpy.complex128, numpy.complex256],
 'others': [bool, object, bytes, str, numpy.void]}

I replaced deprecated code in the imgaug.py as shown in changes below.

Additionally I checked with Ruff (which was advised here) whether there were other issues.

$ ruff check --select NPY201
All checks passed!