Extract yandex cloud auth crate from ydb to separated crate

[sshaplygin]

Hello! i found hardcode IP for YC_METADATA_URL variable from this line. I guess, it is bad practice to save endpoint at sdk library

[rekby]

Hello, Sam.

Thanks for the research.
About IP instead of domain name: It is official URL for yandex cloud: https://yandex.cloud/en/docs/compute/concepts/vm-metadata

About include urls of metadata in common way:
It did for simplify start of work. In the future auth crate will be separated, similar to other SDKs and base crate will not contains any cloud specific.