tests: added output_file_names pgx test

Author: victoraugustolls

internal/endtoend/testdata/output_file_names/pgx/go/db_gen.go

@@ -0,0 +1,17 @@
+{
+  "version": "1",
+  "packages": [
+    {
+      "path": "go",
+      "engine": "postgresql",
+      "driver": "pgx/v4",
+      "name": "querytest",
+      "schema": "query.sql",
+      "queries": "query.sql",
+      "emit_interface": true,
+      "output_db_file_name": "db_gen.go",
+      "output_models_file_name": "models_gen.go",
+      "output_querier_file_name": "querier_gen.go"
+    }
+  ]
+}