chore: using graph node type

[fforbeck]

🥳 Adds

• GRAPH_NODE_TYPE env var to indicate the type of the node that we will be deploying the subgraph to.
• additional env var checks depending on node type deployment

⛔️ Removes

• NETWORK env var

[fforbeck]

@jdville03 While I was testing the subgraph deployment for the new tutorial version I noticed we don't really use the networks, they work as a flag to indicate which graph node we will be deploying to. I refactored that to use a specific node type variable, since the network doesn't really matter as long as we set it correctly in the subgraph attribute. Also, if we use other networks such as: polygon, polygontest, harmony, harmonytest, xdai, etc we would need to update the script every time a new network is added.
wdyt about this approach? am I missing anything here?
thanks

[jdville03]

Thanks for suggesting this. I updated some of the documentation and added more required env var checks depending on the graph node type.