Remove provider checks at startup

[mangas]

Fixes https://github.com/graphprotocol/graph-node/issues/3937

• New chain now created with ChainIdentifier::default() on start
• Adapter genesis+net_version now checked by ProviderManager
• Adapter checks will be disabled temporarily after an intermittent failure
• Adapter won't be returned by the ProviderManager if the ident returned is not the expected value.
• BlockIngestor now takes a ChainClient and tries to get an adapter with each poll, this means it won't stop if the first poll fails
• node/src/main.rs refactored so that most of the init code is automatically executed by the new Networks type.
• graphman run now uses the same init code as the node, should be able to run using any chain
• EthereumNetworks type removed
• FirehoseNetworks type removed

Missing:

• Update ident on first check from new

Future improvements:

• Cache genesis once it's set
• Cache chain ident once it's set