Plugin Support

...G...... [ZBXNEXT-9533] implemented override of config parameters by environment variables

* commit '56a86117a299030ffa972d3cf753d1f650943358':
  ...G...... [ZBXNEXT-9533] added mutex to access set of envitonment variables set
  ...G...... [ZBXNEXT-9533] fixed config filenames in error logs
  ...G...... [ZBXNEXT-9533] improved after code review
  ...G...... [ZBXNEXT-9533] improved finalization after config load
  ...G...... [ZBXNEXT-9533] implemented user parameters reload, improved config load finalization
  ...G...... [ZBXNEXT-9533] implemented override of config parameters by environment variables