node: Refactor config to accept Firehose providers (and made Provider…

… a little bit more extensible) (graphprotocol#2647)

There is a backward compatible handling of config that at some point should be converted to the new syntax form. The new syntax form is

```
{ label = "node0", details = { type = "web3", transport = "rpc", url = "...", features = [...] } }
```

While a Firehose provider now looks like:

```
{ label = "firehose0", details = { type = "firehose", url = "..." } }
```

This is for now undocumented and is first step towards Firehose integration in the codebase directly.

node/resources/tests/full_config.toml

@@ -0,0 +1,68 @@
+[general]
+query = "query_node_.*"
+
+[store]
+[store.primary]
+connection = "postgresql://postgres:1.1.1.1@test/primary"
+pool_size = [
+  { node = "index_node_1_.*", size = 2 },
+  { node = "index_node_2_.*", size = 10 },
+  { node = "index_node_3_.*", size = 10 },
+  { node = "index_node_4_.*", size = 2 },
+  { node = "query_node_.*", size = 10 }
+]
+
+[store.shard_a]
+connection = "postgresql://postgres:1.1.1.1@test/shard-a"
+pool_size = [
+  { node = "index_node_1_.*", size = 2 },
+  { node = "index_node_2_.*", size = 10 },
+  { node = "index_node_3_.*", size = 10 },
+  { node = "index_node_4_.*", size = 2 },
+  { node = "query_node_.*", size = 10 }
+]
+
+[deployment]
+# Studio subgraphs
+[[deployment.rule]]
+match = { name = "^prefix/" }
+shard = "shard_a"
+indexers = [ "index_prefix_0",
+             "index_prefix_1" ]
+
+[[deployment.rule]]
+match = { name = "^custom/.*" }
+indexers = [ "index_custom_0" ]
+
+[[deployment.rule]]
+shard = "shard_a"
+indexers = [ "index_node_1_a",
+             "index_node_2_a",
+             "index_node_3_a" ]
+
+[chains]
+ingestor = "index_0"
+
+[chains.mainnet]
+shard = "primary"
+provider = [
+  { label = "mainnet-0", url = "http://rpc.mainnet.io", features = ["archive", "traces"] }
+]
+
+[chains.ropsten]
+shard = "primary"
+provider = [
+  { label = "ropsten-0", url = "http://rpc.ropsten.io", transport = "rpc", features = ["archive", "traces"] }
+]
+
+[chains.goerli]
+shard = "primary"
+provider = [
+  { label = "goerli-0", url = "http://rpc.goerli.io", transport = "ipc", features = ["archive"] }
+]
+
+[chains.kovan]
+shard = "primary"
+provider = [
+  { label = "kovan-0", url = "http://rpc.kovan.io", transport = "ws", features = [] }
+]