[ENH] Split the library between the product management and the data loading

[remi-braun]

This library features two big sets of features:

• satellite product agnostic handling (automatic recognition of the data type) and metadata reading
• loading data

The first point could be a library on itself, with very lightweight dependency (get rid of SNAP, GDAL (?), etc), useful for some applications that doesn't need any data loading (i.e. just identifying which type of data we have, etc.)

EOReader would stay the complete library, but extracting the features corresponding to the first bullet point could be valuable.