During the update related to Transactions Policies we had to undo the changes made on #1467.

Because of that, we need to improve our API again to enable users to easily get the transaction ID before actually sending the transaction to the node.

We need to address 2 things:

• Add a method to hash the TX on the transaction request classes.
• Reimplement logic to make it possible for users to get the transaction ID before submitting it to the node. This also needs to be easily used by Predicates.