Kakarot's `wallet_addInvokeTransaction` doesn't return the same data format as Starknet wallets

[enitrat]

Starknet connectors return an InvokeFunctionResponse, which is an object like:

type Result = {
  transaction_hash: string,
  ...
}

while Kakarot connectors returns the transaction hash directly.

type Result = string

Also, I believe it would be interesting to return the starknet transaction hash, if possible.
Most apps today are waiting for the transaction status to be accepted on L2 to send a confirmation to the user.
If we return the evm tx hash on kakarot, this never ends.

cc @Eikix

[ooochoche]

@enitrat Can I jump on this?