Update field defaults to Arbitrum One

[alex-pakalniskis]

This issue proposes changing the default value for network_subgraph_endpoint and protocol_network to Arbitrum One (currently set to Ethereum). Indexing rewards are overwhelming distributed on Arbitrum One (95% vs 5% on Ethereum) and will ultimately be entirely on Arbitrum One. Updating this default value will remove a minor, but nonetheless inconvenient, configuration step for Indexers using this tool.

network_subgraph_endpoint

State	Default value
Current	https://api.thegraph.com/subgraphs/name/graphprotocol/graph-network-mainnet
Proposed	https://api.thegraph.com/subgraphs/name/graphprotocol/graph-network-arbitrum

protocol_network

State	Default value
Current	mainnet
Proposed	arbitrum