dev: add sepolia to the list of testnets (kkrt-labs#1051)

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## Pull request type

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- [ ] Bugfix
- [x] Feature
- [ ] Code style update (formatting, renaming)
- [ ] Refactoring (no functional changes, no api changes)
- [ ] Build related changes
- [ ] Documentation content changes
- [ ] Other (please describe):

## What is the current behavior?
Missing sepolia to the list of testnets
<!-- Please describe the current behavior that you are modifying,
or link to a relevant issue. -->

Resolves #NA

## What is the new behavior?
Add sepolia to the list of testnets.

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kakarot_scripts/constants.py

@@ -29,13 +29,22 @@
         "devnet": False,
         "chain_id": StarknetChainId.MAINNET,
     },
-    "testnet": {
-        "name": "testnet",
+    "goerli": {
+        "name": "starknet-goerli",
         "explorer_url": "https://testnet.starkscan.co",
         "rpc_url": f"https://starknet-goerli.infura.io/v3/{os.getenv('INFURA_KEY')}",
         "devnet": False,
         "chain_id": StarknetChainId.GOERLI,
     },
+    "sepolia": {
+        "name": "starknet-sepolia",
+        "explorer_url": "https://sepolia.starkscan.co/",
+        "rpc_url": f"https://starknet-sepolia.infura.io/v3/{os.getenv('INFURA_KEY')}",
+        "devnet": False,
+        "chain_id": StarknetChainId.SEPOLIA_TESTNET,
+        "check_interval": 5,
+        "max_wait": 30,
+    },
     "starknet-devnet": {
         "name": "starknet-devnet",
         "explorer_url": "",

kakarot_scripts/utils/kakarot.py

@@ -262,6 +262,7 @@ async def _wrapper(self, *args, **kwargs):
 async def _contract_exists(address: int) -> bool:
     try:
         await RPC_CLIENT.get_class_hash_at(address)
+        logger.info(f"ℹ️  Contract at address {hex(address)} already exists")
         return True
     except ClientError:
         return False

kakarot_scripts/utils/starknet.py

@@ -100,7 +100,7 @@ async def get_starknet_account(
                 "Client failed with code 40: Contract error." in message
                 or "Client failed with code 40: Requested entry point was not found."
                 in message
-                or "Client failed with code 21: Invalid message selector." in message
+                or "Invalid message selector." in message
                 or "StarknetErrorCode.ENTRY_POINT_NOT_FOUND_IN_CONTRACT" in message
                 or ("code 40" in message and "not found in contract" in message)
             ):