chain, graph: Remove old FromStr implementation to parse declared calls

We can't use FromStr any more since we need to pass the spec version and
ABI to the parser. Also, adapt some of the old tests to the new parser and
streamline them a little.

Author: lutter

chain/ethereum/src/data_source.rs

@@ -1504,20 +1504,15 @@ impl UnresolvedMappingEventHandler {
     }
 }
 
-#[derive(Clone, Debug, Hash, Eq, PartialEq, Deserialize)]
+#[derive(Clone, Debug, Hash, Eq, PartialEq)]
 pub struct MappingEventHandler {
     pub event: String,
     pub topic0: Option<H256>,
-    #[serde(deserialize_with = "deserialize_h256_vec", default)]
     pub topic1: Option<Vec<H256>>,
-    #[serde(deserialize_with = "deserialize_h256_vec", default)]
     pub topic2: Option<Vec<H256>>,
-    #[serde(deserialize_with = "deserialize_h256_vec", default)]
     pub topic3: Option<Vec<H256>>,
     pub handler: String,
-    #[serde(default)]
     pub receipt: bool,
-    #[serde(default)]
     pub calls: CallDecls,
 }