Adds operator service to run using PM2 for auto restart from crash, steps.

1. Install PM2 process manager link https://pm2.keymetrics.io/
2. Compiler or install from release eg operator-service-macos
3. Add operator service to PM2 using below command pm2 start operator-service-macos -- -wallet-key 0xxafsfasfasfasf.....
4. Check the status and logs of PM2 using pm2 ls & pm2 logs.