feat: Integrate Aggregator in HelloWorldServiceManager

[afkbyte]

This PR contains only the changes to the HelloWorldServiceManager required to integrate with an aggregator service.

• Added address public aggregator to store the aggregator's address
  • implemented onlyAggregator modifier to restrict task response
• Modified respondToTask function to:
  • Accept aggregated signature data
  • Verify signatures using ECDSAStakeRegistry
  • Check if all signers are registered operators
  • Store aggregated response data
• update deploy scripts

[wesfloyd]

Reminder for Steven and Wes: might warrant a point release when ready.