Incompatibilities with NumPy 2.0

PySpark references some code which was removed with NumPy 2.0.

 python/pyspark/pandas/strings.py:

• np.NaN was removed, should be replaced with np.nan

python/pyspark/pandas/typedef/typehints.py

• np.string_ was removed, is an alias for np.bytes_
• np.float_ was removed, is defined the same as np.double
• np.unicode_ was removed, is an alias for np.str_