refactor: add use fallback decorator

[JuArce]

Changes

1. Add decorators to implement fallback mechanism for RPCs
   a. Add use_fallback(rpc_nodes, logger, error_message="Failed") decorator for sync functions.
   b. Add use_async_fallback(rpc_nodes, logger, error_message="Failed") for async functinos.
   Methods that use this decorator must receive as last parameter the rpc_node. Ie

@use_async_fallback(rpc_nodes, logger, "Failed to sign invoke transaction")
async def sign_invoke_transaction(call: Call, max_fee: int, rpc_node=main_rpc_node):
    return await rpc_node.account.sign_invoke_transaction(call, max_fee=max_fee)

This refactor keeps separate fallback mechanism from methods logic improving the code readability.

2. Added two classes that contains client, account and contract to work with the RPC

class EthereumRpcNode:
    def __init__(self, rpc_url, private_key, contract_address, abi):
        self.w3 = Web3(Web3.HTTPProvider(rpc_url))
        self.account = self.w3.eth.account.from_key(private_key)
        self.contract = self.w3.eth.contract(address=contract_address, abi=abi)

class StarknetRpcNode:
    def __init__(self, rpc_url, private_key, wallet_address, contract_address, chain_id):
        self.full_node_client = MmFullNodeClient(node_url=rpc_url)
        key_pair = KeyPair.from_private_key(key=private_key)
        self.account = Account(
            client=self.full_node_client,
            address=wallet_address,
            key_pair=key_pair,
            chain=chain_id,
        )
        self.contract_address = contract_address

[rcatalan98]

It's a huge improvement in readability congrats! Just left a small comment.