scripts: pytest: align adapters API

Select and place common code of three adapters (HardwareAdapter,
BinaryAdapterBase and QemuAdapter) into basic DeviceAdapter class.

Introduce new way of reading device output by run separate thread which
try to read device output and place it into internal python queue.
Thanks to this, now it is possible to create readline method for all
adapters, which can be unblock when timeout occur.

Collect all common steps which have to be done before setup device in
launch method. The same was done for teardown operations which were
placed into close method.

Additionally some protection mechanisms were introduced to prevent for
undesirable side-effects when user could try to launch to already
launched device or try to send some data to disconnected device.

iter_stdout method was replaced by two new methods: readline and
readlines. To make it possible to remove all read output from internal
buffer (queue), clear_buffer method was introduced.

Also unit tests were rewritten to work properly with current version
of adapters.

Signed-off-by: Piotr Golyzniak <piotr.golyzniak@nordicsemi.no>