Implement new noise models

[ninamiolane]

What?

• Implement new noise models within the cryo-EM image formation model.
• Add details about the structure of the config input to the docstrings of the simSPI/linear_simulator/noise_utils.py module.
• Add corresponding unit-tests.
• Use pre-commit (see README) to make sure that your code follows style guidelines.

Why?

Cryo-EM images have very interesting noise models.

The community needs to be able to experiment with different types of noise, beyond the white Gaussian noise model currently implemented.

Where?

• The Noise class is located in the simSPI/linear_simulator/noise_utils.py module.
• The unit-tests are here.

How?

• Rename the noise_utils.py module into noise.py and make sure the unit-tests and notebooks run.
• Allow the config input to the Noise class to have a space key, where the value will be either image or fourier.
• Rename current forward method into a private _forward_white_gaussian method.
• Create a _forward_[new_noise_model] method, with the projection operation in fourier space.
• Create a forward method that calls either _forward_white_gaussian or _forward_[new_noise_model] depending on the value in the self.config attribute.

Details on the cryo-EM image formation models can be found in Donnat et al 2022.