Initial plugin implementation

* refactor packages, flags, subscriptions
* DRY refactor builder tests
* use mockgen to generate mocks
* update README
* MODE=statediff no longer needed for unit tests
* simplify func names, clean up metrics
* move write params to service field
* sql indexer: confirm quit after ipld cache reset
  prevents negative waitgroup panic
* don't let TotalDifficulty become nil
* use forked plugeth, plugeth-utils for now

test/compose.yml

@@ -0,0 +1,27 @@
+version: "3.2"
+
+services:
+  migrations:
+    restart: on-failure
+    depends_on:
+      - ipld-eth-db
+    image: git.vdb.to/cerc-io/ipld-eth-db/ipld-eth-db:v5.0.2-alpha
+    environment:
+      DATABASE_USER: "vdbm"
+      DATABASE_NAME: "cerc_testing"
+      DATABASE_PASSWORD: "password"
+      DATABASE_HOSTNAME: "ipld-eth-db"
+      DATABASE_PORT: 5432
+
+  ipld-eth-db:
+    image: timescale/timescaledb:latest-pg14
+    restart: always
+    command: ["postgres", "-c", "log_statement=all"]
+    environment:
+      POSTGRES_USER: "vdbm"
+      POSTGRES_DB: "cerc_testing"
+      POSTGRES_PASSWORD: "password"
+    ports:
+      - "127.0.0.1:8077:5432"
+    volumes:
+      - ../indexer/database/file:/file_indexer