Network config override for Substreams manifests

[jubeless]

SUBSTREAMS_ENDPOINTS_CONFIG_POLYGON=polygonl.friend.com:443
SUBSTREAMS_ENDPOINTS_CONFIG_MAINNET=ethmainn.friend.com:443

To support: substreams run myfile.polygon.yaml and: substreams run myfile.yaml // where network is mainnet myfile.polygon.yaml:

network: polygon
#network: mumbai
#network: goerli
#network: goerli
#network: eip1544

Align with: https://thegraph.com/docs/en/developing/supported-networks/

1. SUBSTREAMS_ENDPOINTSCONFIG[network] and defined in the manifest. (this is what needs implementing)
2. SUBSTREAMS_ENDPOINT viper-based config
3. -e value
4. default -e value (remove the default value, issue a deprecation notice)
   • Error: missing endpoint, specify -e or SUBSTREAMS_ENDPOINTS_CONFIG_[network] as defined in network field of the Substreams manifest.

[sduchesneau]

• Substreams will have a hardcoded map of 'network -> endpoint' to use if the environment variables are not used. It will point to all streamingfast's endpoints, or Pinax for the ones that we don't support but they do (ex: antelope)
• This hardcoded map will come with a "TODO" comment saying that this is temporary until we have something "distributed" (like, the gateway advertising available endpoints or whatever)
• If a substreams manifest does not specify the 'Network', the default is to consider it to be mainnet.
• the -e flag always overrides this whole mechanism

The idea is also that the 'subservicesd' component, where we deploy, will use those values...