op-service: add gnosis safe client (#16629)

* gnosis: add safe client

* gnosis: add integration tests

* gnosis: remove justfile, contain all tests in go

* gnosis: fix linter errors

* gnosis: always build contracts during test setup

Author: bitwiseguy

op-service/gnosis/abi.go

@@ -0,0 +1,47 @@
+package gnosis
+
+var safeABIString = `[
+    	{
+        	"inputs": [],
+        	"name": "getOwners",
+        	"outputs": [{"internalType": "address[]", "name": "", "type": "address[]"}],
+        	"stateMutability": "view",
+        	"type": "function"
+    	},
+    	{
+        	"inputs": [{"type": "address", "name": "owner"}],
+        	"name": "isOwner",
+        	"outputs": [{"type": "bool", "name": ""}],
+        	"stateMutability": "view",
+        	"type": "function"
+    	},
+        {
+            "inputs": [
+                {"type": "address", "name": "to"},
+                {"type": "uint256", "name": "value"},
+                {"type": "bytes", "name": "data"},
+                {"type": "uint8", "name": "operation"},
+                {"type": "uint256", "name": "safeTxGas"},
+                {"type": "uint256", "name": "baseGas"},
+                {"type": "uint256", "name": "gasPrice"},
+                {"type": "address", "name": "gasToken"},
+                {"type": "address", "name": "refundReceiver"},
+                {"type": "bytes", "name": "signatures"}
+            ],
+            "name": "execTransaction",
+            "outputs": [{"type": "bool", "name": "success"}],
+            "type": "function"
+        },
+        {
+            "inputs": [],
+            "name": "nonce",
+            "outputs": [{"type": "uint256", "name": ""}],
+            "type": "function"
+        },
+        {
+            "inputs": [],
+            "name": "getThreshold",
+            "outputs": [{"type": "uint256", "name": ""}],
+            "type": "function"
+        }
+    ]`