Where in the presentation request to include transaction_data objects

[Sakurann]

(separating a discussion started in #156 (comment) into a new issue)

On a May-14-2024 WG call, there seems to be a rough consensus that transaction_data should be outside the input_descriptor objects and should contain reference to the input_descriptors that are requesting credentials to which the content of a transaction_data can be bound to (instead of putting transaction data obejct inside an input_descriptor, which was an original idea). This updated approach would prevent duplication of the same transaction data object across multiple input descriptors when the verifier is asking to "bind transaction_data to credential A or credential B".

opening an issue to make sure there is a consensus on this direction, expecting to be able to close this issue relatively soon.