SDK standardization, FlatBuffer support

[DadiBit]

Description

Standardize SDKs across all languages.

Describe the solution you'd like

Move all SDKs to open-meteo/sdk with the integration of the FlatBuffer library (currently not available for .NET).
Standardize SDK methods and classes names and structures.

Additional context

I would kindly like to ask you some input on the related issue on the open-meteo-website repo. We're in an early stage of development, so changes can still happen: it's the tight time to find out what could work best for this library/language (if at all possible), in order to make it feasible to standardize all SDKs.