Instead of splitting up the transports into capabilities, we compose
them directly for each application. This allows us to remove the
websocket transport for the CLI which is really only needed for the
ASB to allow retrieval of quotes via the browser.
Introduces a minimum buy Bitcoin amount similar to the maximum amount already present.
For the CLI the minimum amount is enforced by waiting until at least the minimum is available as max-giveable amount.
What goes over the wire should not be coupled to the errors being printed.
For the CLI and ASB we introduce a separate error enum that is used for logging.
When sending over the wire the errors are mapped to and from the `network::spot_price::Error`.
As part of Bob-specific spot_price code was moved from the network into bob.
Clearly separation of the network API from bob/alice.
Move Alice's spot price logic into a dedicated network behaviour that handles all the logic.
The new behaviour encapsulates the complete state necessary for spot price request decision making.
The network behaviour cannot handle asynchronous calls, thus the balance is managed inside the spot price and has to updated regularly from the outside to ensure the spot price balance check has up to date data.
At the moment the balance is updated upon an incoming quote requests.
Code that is relevant for both ASB and CLI remains in the `network::spot_price` module (e.g. `network::spot_price::Error`).
This PR does a few things.
* It adds a TorTransport which either dials through Tor's socks5 proxy or via clearnet.
* It enables ASB to register hidden services for each network it is listening on. We assume that we only care about different ports and re-use the same onion-address for all of them. The ASB requires to have access to Tor's control port.
* It adds support to dial through a local Tor socks5 proxy. We assume that Tor is always available on localhost. Swap cli only requires Tor to be running so that it can send messages via Tor's socks5 proxy.
* It adds a new e2e test which swaps through Tor. For this we assume that Tor is currently running on localhost. All other tests are running via clear net.
