This commit adds support for including a `kernel.yaml` as
meta/kernel.yaml in the snap. This will help the pi-kernel
to ship their DTBs as part of the kernel snap.
- a new Authorization component to generate requests.
- Auth and token discharge logic tied to Authorization class.
- Refresh logic centralized to the request of the Authorization class
(as it is backend specific).
- Core login primitives simplified in StoreClient and relevant
delegations to the Authorization class.
- A general simple inheritable requests wrapper for each .*API class
with an abstractmethod to implement the request logic.
There is one big change in behavior, internally mostly, is that now
all requests to get_account_information are not stored anymore. This
affects a fast whoami call. This will be added back after the new
candid client is introduced.
