Closes #26667
To be eligible for fee-bumping, a transaction must not have any of its outputs (eg - change) spent in other unconfirmed transactions in the wallet. This behavior is currently enforced and tested.
However, this check shouldn’t apply to spends in abandoned descendant transactions, as explained by #26667.
CWallet::IsSpent
already carves out an exception for abandoned transactions, so we can just use that.
I’ve also added a new test to cover this case.