E2E tests for existing endpoints related to beacon namespace

[nidhi-singh02]

Implement E2E tests for existing endpoints and correct if deviates from spec. For any not present in eth2client, skip for now.

• beacon / GetStateRoot - working
• beacon / GetStateFork - working
• beacon / GetStateValidators - Not present in eth2client
• beacon / PostStateValidators - working, for this to work fully, implement /eth/v2/debug/beacon/states/%s
• beacon / GetStateValidator - Not present in eth2client
• beacon / GetStateValidatorBalances - Not present in eth2client
• beacon / PostStateValidatorBalances - working
• beacon / GetBlockRewards - Not present in eth2client
• beacon / GetRandao - working

[nidhi-singh02]

https://github.com/berachain/beacon-kit/pull/1983