fetch_beneficiaries/2 works with all reward types

Why:

* For the indexer to update block reward contract beneficiaries for all
types (e.g. block, external, uncle, etc). For details on Parity's reward
types please see:
0f90696528/rpc/src/v1/types/trace.rs (L299-L308)
* Issue link: https://github.com/poanetwork/blockscout/issues/767

apps/ethereum_jsonrpc/lib/ethereum_jsonrpc/parity.ex

@@ -74,7 +74,7 @@ defmodule EthereumJSONRPC.Parity do
 
   defp extract_beneficiaries(traces) when is_list(traces) do
     Enum.reduce(traces, MapSet.new(), fn
-      %{"action" => %{"rewardType" => "block", "author" => author}, "blockNumber" => block_number}, beneficiaries ->
+      %{"type" => "reward", "blockNumber" => block_number, "action" => %{"author" => author}}, beneficiaries ->
         beneficiary = %{
           block_number: block_number,
           address_hash: author

apps/ethereum_jsonrpc/test/ethereum_jsonrpc/parity_test.exs

@@ -294,6 +294,64 @@ defmodule EthereumJSONRPC.ParityTest do
       assert fetched_beneficiaries == expected_beneficiaries
     end
 
+    test "with 'external' 'rewardType'", %{
+      json_rpc_named_arguments: json_rpc_named_arguments
+    } do
+      block_number = 5_609_295
+      block_quantity = EthereumJSONRPC.integer_to_quantity(block_number)
+      hash1 = "0xe8ddc5c7a2d2f0d7a9798459c0104fdf5e987aca"
+      hash2 = "0x523b6539ff08d72a6c8bb598af95bf50c1ea839c"
+
+      if json_rpc_named_arguments[:transport] == EthereumJSONRPC.Mox do
+        expect(EthereumJSONRPC.Mox, :json_rpc, fn %{params: [^block_quantity]}, _options ->
+          {:ok,
+           [
+             %{
+               "action" => %{
+                 "author" => hash1,
+                 "rewardType" => "external",
+                 "value" => "0xde0b6b3a7640000"
+               },
+               "blockHash" => "0xf19a4ea2bb4f2d8839f4c3ec11e0e86c29d57799d7073713958fe1990e197cf5",
+               "blockNumber" => 5_609_295,
+               "result" => nil,
+               "subtraces" => 0,
+               "traceAddress" => [],
+               "transactionHash" => nil,
+               "transactionPosition" => nil,
+               "type" => "reward"
+             },
+             %{
+               "action" => %{
+                 "author" => hash2,
+                 "rewardType" => "external",
+                 "value" => "0xde0b6b3a7640000"
+               },
+               "blockHash" => "0xf19a4ea2bb4f2d8839f4c3ec11e0e86c29d57799d7073713958fe1990e197cf5",
+               "blockNumber" => 5_609_295,
+               "result" => nil,
+               "subtraces" => 0,
+               "traceAddress" => [],
+               "transactionHash" => nil,
+               "transactionPosition" => nil,
+               "type" => "reward"
+             }
+           ]}
+        end)
+      end
+
+      expected_beneficiaries =
+        MapSet.new([
+          %{block_number: block_number, address_hash: hash2},
+          %{block_number: block_number, address_hash: hash1}
+        ])
+
+      {:ok, fetched_beneficiaries} =
+        EthereumJSONRPC.Parity.fetch_beneficiaries(5_609_295..5_609_295, json_rpc_named_arguments)
+
+      assert fetched_beneficiaries == expected_beneficiaries
+    end
+
     test "with no rewards, returns {:ok, []}", %{
       json_rpc_named_arguments: json_rpc_named_arguments
     } do
@@ -309,7 +367,7 @@ defmodule EthereumJSONRPC.ParityTest do
       end
     end
 
-    test "with nil rewards, returns {:error, }", %{
+    test "with nil rewards, returns {:error, reason}", %{
       json_rpc_named_arguments: json_rpc_named_arguments
     } do
       if json_rpc_named_arguments[:transport] == EthereumJSONRPC.Mox do