Refactor/3.0/coordinator client (#2348)

* deduplicate migrateOnceAsync() test helper

* move and rename coordinator client to @0x/contracts-coordinator

contracts/test-utils/package.json

@@ -44,6 +44,7 @@
     "dependencies": {
         "@0x/assert": "^2.2.0-beta.2",
         "@0x/base-contract": "^5.5.0-beta.3",
+        "@0x/contract-addresses": "^3.3.0-beta.4",
         "@0x/dev-utils": "^2.4.0-beta.3",
         "@0x/json-schemas": "^4.1.0-beta.2",
         "@0x/order-utils": "^8.5.0-beta.3",