[backport#16512] rpc: Shuffle inputs and outputs after joining psbts
Summary:
Pull request description:
`joinpsbts` currently just adds the inputs and outputs in the order of that the PSBTs were provided. This makes it extremely easy to identify which outputs belong to which inputs. This PR changes that so that all of the inputs and outputs are shuffled in the joined transaction.
Backport of Core PR16512
Test Plan:
ninja ./test/functional/test_runner.py rpc_psbt
Reviewers: #bitcoin_abc, Fabien
Reviewed By: #bitcoin_abc, Fabien
Subscribers: Fabien
Differential Revision: https://reviews.bitcoinabc.org/D6665