climetlab is not numpy 2 compliant (numpy.NaN is deprecated)

[thebaptiste]

What happened?

I tried to use climetlab with numpy 2.0.2 on Python 3.12
import climetlab fails because numpy.NaN is used in hurricane_database.py
I used release 0.20.1 but it would have been the same with more recent releases as this is not fixed (I couldn't use 0.24.0 because of issue #69)

What are the steps to reproduce the bug?

Build climetlab from sources with numpy 2.0.2
Then use it with a program using hurricane_database.py

Version

v0.20.1

Platform (OS and architecture)

RockyLinux 8

Relevant log output

`  File "/src/integration_tests/0010_climetlab/climetlab_test.py", line 6, in <module>
    atlantic = cml.load_dataset("hurricane-database", bassin="atlantic")
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/metwork-mfext-experimental_numpy2/opt/python3_scientific/lib/python3.12/site-packages/climetlab/datasets/__init__.py", line 280, in load_dataset
    ds = klass(*args, **kwargs).mutate()
         ^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/metwork-mfext-experimental_numpy2/opt/python3_scientific/lib/python3.12/site-packages/climetlab/core/__init__.py", line 25, in __call__
    obj.__init__(*args, **kwargs)
  File "/opt/metwork-mfext-experimental_numpy2/opt/python3_scientific/lib/python3.12/site-packages/climetlab/datasets/hurricane_database.py", line 101, in __init__
    pressure = np.NaN if line[43] == "-" else float(line[43:47])
               ^^^^^^
  File "/opt/metwork-mfext-experimental_numpy2/opt/python3_scientific/lib/python3.12/site-packages/numpy/__init__.py", line 397, in __getattr__
    raise AttributeError(
AttributeError: `np.NaN` was removed in the NumPy 2.0 release. Use `np.nan` instead.. Did you mean: 'nan'?``

Accompanying data

No response

Organisation

Meteo-France