* cleanup: remove CFFI deltachat bindings usage, and consolidate test support with rpc-bindings
major simplification: all chatmail fixtures used in the test are now created inside the cmdeploy plugin,
and do not inherit anything from other fixture machineries, let alone the legacy deltachat CFFI ones.
also fix that pytest report headers show correct chatmail domains under test
* drastically reduce round-trips for dns checks, and do it during 'run' and 'dns' sub commands
* provide progress-dots for dns checks and "--verbose" for seeing what is executed remotely
* introduce ssh-mediated remote python function execution mechanism
