Feature gate withdrawals (#3684)

* start feature gating

* feature gate withdrawals

beacon_node/execution_layer/Cargo.toml

@@ -4,6 +4,9 @@ version = "0.1.0"
 edition = "2021"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+[features]
+withdrawals = ["state_processing/withdrawals", "types/withdrawals"]
+withdrawals-processing = ["state_processing/withdrawals-processing"]
 
 [dependencies]
 types = { path = "../../consensus/types"}