cephadm: Replace execnet (and remoto)
Pull request ID:
[[https://github.com/pytest-dev/execnet]] is in maintenance mode.
execnet currently is in maintenance-only mode, mostly because it is still the backend of the pytest-xdist plugin. Do not use in new projects.
For pacific, we should replace it.
For the GSOC / Outreachy project, see https://pad.ceph.com/p/project-replace-cephadm-execnet