Use config replace logic instead of reinstalling service in switch

[michalpristas]

Describe the enhancement:

At the moment we do following flow when switching priviledged mode of agent:

• change permissions and other related tasks
• uninstall service
• remove service
• install service
• start service

DoD for this issue is:

• Following flow
  • change permissions and other related tasks
  • replace config
  • restart service
• Following mechanisms used for config change
  • Windows: calling windowsService.UpdateConfig
  • Systemd/Darwin: modification of a service file

[elasticmachine]

Pinging @elastic/elastic-agent-control-plane (Team:Elastic-Agent-Control-Plane)