Establishing a single interface in and out of the library (Using Formats for all data input and output)

[Atahanak]

Currently, the preprocessing functions either return a Format * or a CPP native type. Even though it may be relatively easier for the user to get the native types and use them directly, it raises some questions concerning the coherency of the library. The following are some advantages of establishing Format * as the medium of exchange between the user and the library.

1. Users know what to expect from and what to input to the library.
2. Utilities like FeatureExtractor and Experiments benefit from this update and can switch to Format * instead of std::any.
3. Additional information like size etc., is stored in Format * but not native types. This is especially useful if the returned object's size is unknown beforehand.

We already needed and used a similar solution with CUDAArray.