simplify light client contract: create genesis state struct and remove states mapping

[alysiahuggins]

subtask of #1912

1. remove unnecessary variables from the LightClientState

struct LightClientState {
        uint64 viewNum;
        uint64 blockHeight;
        BN254.ScalarField blockCommRoot;
}

2. introduce a new struct for genesis state

struct GenesisState {
        uint256 threshold;
        uint256 stakeTableBlsKeyComm;
        uint256 stakeTableSchnorrKeyComm;
        uint256 stakeTableAmountComm;
        uint256 blockCommRoot;
 }

To ensure simplicity for the updateStateHistory(uint64 blockNumber, uint64 blockTimestamp, LightClientState memory state) function, there may be need for the genesisState to be separated into two separate variables e.g.

struct LightClientState {
        uint64 viewNum;
        uint64 blockHeight;
        BN254.ScalarField blockCommRoot;
}

struct StakeState {
        uint256 threshold;
        BN254.ScalarField stakeTableBlsKeyComm;
        BN254.ScalarField stakeTableSchnorrKeyComm;
        BN254.ScalarField stakeTableAmountComm;
}
   
StakeStake genesisStake;
LightClientState genesisState;
LightClientState lightClientState;

3. remove the states mapping and add a genesisState variable and add a finalizedState variable