Addressing issue #753 by adding feature mapping for the Fourier Encoder

[mobra7]

Fix for issue #753 :

• FourierEncoder (which is used in IceMix model) previously assumed a specific structure for the feature dimension, which caused issues with certain datasets (e.g. using standard FEATURES.ICECUBE86).
• Now, FourierEncoder accepts a simple list of int or None to map the corresponding features of the data to the features used in FourierEncoder.
• The Fourier mapping can be passed during the initialization of the DeepIce model. Specifying n_features is no longer required.

Minor Fixes:

• Fixed small typos within IceMixNodes.

[RasmusOrsoe]

@mobra7 The problem with pre-commit is now fixed in main. If you update the branch, the failing checks in this PR is likely to pass (see #760).

[Aske-Rosted]

Due to inactivity this PR will be closed, #753 will remain open for a future PR