Harmonize parameters in list_models, list_datasets and list_spaces

[Wauplin]

Feedback from #1146:
=> we are using both snake_case (fetch_config) and camelCase (securityStatus, cardData, lastModified) in the naming. This is surely done to match the backend naming but it makes huggingface_hub inconsistent.

Feeback from @Narsil (on slack - internal link):

• list_models(filter=ModelFilter(filter=ModelSearchArguments().library.Transformers) feels weird to write
• using direction was not obvious when using sort (list_models(sort="downloads")) (from @Wauplin : maybe using sort="-downloads") ?)
• the sort options refers to all attributes of ModelInfo but all of them are not explicitly defined ("downloads" for example) => maybe we could enforce ModelInfo to define most up to date attributes ?
• It felt weird to use a string "downloads" for sort, and an enum for filter
• I would have imagined that the options as enums would all have been directly importable from the lib (not sure if feasible or if gotten dynamicaly from the hub)
• I would have imagined able to use all strings everywhere (and be yelled at if the string was invalid with potential options).
• I didn't need but expected more complex options like and or mecanism for filtering.

Feedback from @Wauplin :

• initilializing ModelSearchArguments() or DatasetSearchArguments() takes a long time since it requires to first list all models/datasets from the Hub. Kinda niche problem but it feels weird to loop through all models before making a search request to the Hub. => maybe we could still have this but promote the string-based method ?

All of this might not be tackled in a single PR but I'm dropping them all at once since they are related to the same topic.

[Wauplin]

Feedback from @nbroad1881 (on slack - internal link):

• When I do [x for x in list_models(search="bert") if x.tags is not None] I get an empty list which means they all have None for the tags => have to set full=True.
• Example in docs is broken. Update from @osanseviero: When using list_models with no filter, you don't get the full results. When using a filter you do get all the information (including tags) => so example is not broken (but behavior is not intuitive)
• the full keyword should probably be mentioned on this page