[libparsec] generate_new_device is too broad and should be replaced by usage-specifc methods

[AureliaDolo]

I think this generate_new_device is too broad and we should instead replace it with multiple methods, each dedicated to a narrow usecase (especially since it naming is error prone, as we don't know if it means a new device for an existing or for a new user ^^).

from_existing_device_for_user is a good step in that direction (though I would rename this new_device_for_user)

So we can also add new_user that should be use when creating the first device for a user.

What do you think ?

Originally posted by @touilleMan in #8585 (comment)

[AureliaDolo]

• recovery device
• claim device
• bootstrap organization