Upgrade to python3.12 blocked

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Currently the dependencies of the used packages by ece2cmor3 prevent the use of python3.12 (currently 3.12.5).

With:

mamba install python=3.12

It appears that (at least) the pyngl package causes this blocking because this package lacks further support:

mamba install python=3.12

Looking for: ['python=3.12']

conda-forge/linux-64                                        Using cache
conda-forge/noarch                                          Using cache
Could not solve for environment specs
The following packages are incompatible
├─ pyngl is installable with the potential options
│  ├─ pyngl 1.6.1 would require
│  │  └─ python_abi 3.11.* *_cp311, which can be installed;
│  ├─ pyngl [1.5.0|1.5.0_beta20161122|1.6.0|1.6.1] would require
│  │  └─ python [2.7* |>=2.7,<2.8.0a0 ], which can be installed;
│  ├─ pyngl [1.6.0|1.6.1] would require
│  │  └─ python >=3.5,<3.6.0a0 , which can be installed;
│  ├─ pyngl [1.6.0|1.6.1] would require
│  │  └─ python >=3.6,<3.7.0a0 , which can be installed;
│  ├─ pyngl 1.6.1 would require
│  │  └─ python_abi 3.10.* *_cp310, which can be installed;
│  ├─ pyngl 1.6.1 would require
│  │  └─ python >=3.7,<3.8.0a0 , which can be installed;
│  ├─ pyngl 1.6.1 would require
│  │  └─ python_abi 3.7.* *_cp37m, which can be installed;
│  ├─ pyngl 1.6.1 would require
│  │  └─ python >=3.8,<3.9.0a0 , which can be installed;
│  ├─ pyngl 1.6.1 would require
│  │  └─ python_abi 3.8.* *_cp38, which can be installed;
│  └─ pyngl 1.6.1 would require
│     └─ python_abi 3.9.* *_cp39, which can be installed;
└─ python 3.12**  is not installable because there are no viable options
   ├─ python [3.12.0|3.12.1|...|3.12.5] would require
   │  └─ python_abi 3.12.* *_cp312, which conflicts with any installable versions previously reported;
   └─ python 3.12.0rc3 would require
      └─ _python_rc, which does not exist (perhaps a missing channel).

This was already for seen in #731. And indeed it looks like that the interpolation from models level to pressure levels must be able to implement without using the pyngl package. And this interpolation is really the only thing which is used from the pyngl package.