Decouple GQL client for CL node (#2459)

Author: skudasov

framework/.changeset/v0.15.3.md

@@ -0,0 +1 @@
+- Copy GQL client from core's SDK to use without direct import in tests

framework/clclient/gql/README.md

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+## GQL SDK
+
+This client is copied from [core](https://github.com/smartcontractkit/chainlink/tree/develop/deployment/environment/web/sdk) so we can use it without directly importing `chainlink/v2` in any projects which run CL node.
+
+```bash
+go run generate.go
+```