feat: faster and simpler DNS checks, better ip-address determination (#346)

* 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

cmdeploy/pyproject.toml

@@ -18,6 +18,7 @@ dependencies = [
   "ruff",
   "pytest",
   "pytest-xdist", 
+  "execnet",
   "imap_tools",
 ]