Add TACo operators support

[manumonti]

These changes will create a new entity in subgraph: TACoOperator.

TACoOperator will track the current status of each TACoOperator:

• Staking provider address
• Operator address
• Timestamp in which the operator was bonded.
• Timestamp in which the operator was confirmed.
• Timestamp in which the staking provider had a bonded operator for first time.
• Timestamp in which the staking provider had a confirmed operator for first time.

This data is collected using the events BondedOperator and ConfirmedOperator.

This PR will close #37.

[vzotova]

Just a reminder: confirmations in mainnet TACo app will be ready only when proof bot will be working, so far this data only on Polygon

[manumonti]

Just a reminder: confirmations in mainnet TACo app will be ready only when proof bot will be working, so far this data only on Polygon

Right, I'm going to modify this subgraph deleting confirmation events and to create a new subgraph for Polygon.

Thanks!