should `tx_type` be in `FunctionCallDefinition`?

We currently use a CLI flag to set the tx type (legacy, eip1559, eip7702, ...). This kind of limits the flexibility of a scenario; all transactions from it have to be the same type.

If we move `tx_type` to `FunctionCallDefinition`, we can specify a tx type per transaction.
The default type can remain eip1559, but I think we should still support tx-type overrides (e.g. users who want to send legacy txs instead of eip1559).
Given that, the CLI flag can stay, but its purpose would be to override the tx type, so it should be changed to an `Option`.

Posing this as a question to gather feedback. May convert to a feature request later.