GitLab

* `middlewared.utils.functools` -> `middlewared.utils.functools_`

* Get rid of `Popen` in `wireguard.py`

* Get rid of `Popen` in `init_shutdown_script.py`

* Create a global `+io_thread_pool_executor`

* Get rid of `Popen` in `bootenv.py`

* `test_02_create_be_duplicate_name`

* Get rid of `Popen` in `kerberos.py` (not tested)

* Get rid of `Popen` in `smb.py`

* Get rid of `Popen` in `smb_/passdb.py` (not tested)

* Get rid of `Popen` in `system/lifecycle.py`

* Make `run` use thread pool

* Explain `Too many open files` error