support for user and group lists changes

[ldegio]

Changes in the machine list of users should be detected (for example by polling the user list every 30 seconds) and the list should be updated in the libsinsp state.

Also, a new user list block should be added to the dump file if dump to disk is enabled. This means that the dump file read code should handle user list blocks in the middle of event blocks.

[github-actions[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.