This fixes the breakage introduced by transport reshuffles.
It's still not great and I'd love to see context manager based sessions.
But it's good enough for now.
This commit breaks session handling (which matters with Bridge) and
regresses Bridge to an older code state. Both of these issues will be
rectified in subsequent commits.
Explanation of this big API reshuffle follows:
* protocols are moved to trezorlib.transport, and to a single common file.
* there is a cleaner definition of Transport and Protocol API (see below)
* fully valid mypy type hinting
* session handle counters and open handle counters mostly went away. Transports
and Protocols are meant to be "raw" APIs; TrezorClient will implement
context-handler-based sessions, session tracking, etc.
I'm calling this a "reshuffle" because it involved very small number of
code changes. Most of it is moving things around where they sit better.
The API changes are as follows.
Transport is now a thing that can:
* open and close sessions
* read and write protobuf messages
* enumerate and find devices
Some transports (all except bridge) are technically bytes-based and need
a separate protocol implementation (because we have two existing protocols,
although only the first one is actually used). Hence a protocol superclass.
Protocol is a thing that *also* can:
* open and close sessions
* read and write protobuf messages
For that, it requires a `handle`.
Handle is a physical layer for a protocol. It can:
* open and close some sort of device connection
(this is distinct from session! Connection is a channel over which you can
send data. Session is a logical arrangement on top of that; you can have
multiple sessions on a single connection.)
* read and write 64-byte chunks of data
With that, we introduce ProtocolBasedTransport, which simply delegates
the appropriate Transport functionality to respective Protocol methods.
hid and webusb transports are ProtocolBasedTransport-s that provide separate
device handles. HidHandle and WebUsbHandle existed before, but the distinction
of functionality between a Transport and its Handle was unclear. Some methods
were moved and now the handles implement the Handle API, while the transports
provide the enumeration parts of the Transport API, as well as glue between
the respective Protocols and Handles.
udp transport is also a ProtocolBasedTransport, but it acts as its own handle.
(That might be changed. For now, I went with the pre-existing structure.)
In addition, session_begin/end is renamed to begin/end_session to keep
consistent verb_noun naming.
