Rewards mainnet demo

[8sunyuan]

Why are these changes needed?

Example upgrade script for mainnet EigenLayer contracts for the Rewards Release. The EigenLayer RewardsCoordinator is deployed at 0x7750d328b314EfFa365A0402CcfD489B80B0adda

Checks

• [X] I've made sure contracts build and tested scripts on local Anvil
• [X] I've made sure that eigenlayer-middleware points to release tag v0.2.1-mainnet-rewards
• Testing Strategy
  • [ ] Unit tests
  • [ ] Integration tests
  • [ ] This PR is not tested :(