txorphange: move orphan workset to txorphanage

Summary:
Partial backport of core#26295:
https://github.com/bitcoin/bitcoin/pull/26295/commits/3614819864a84ac32f6d53c6ace79b5e71bc174a

Depends on D16231.

Test Plan:

ninja all check-all

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Subscribers: PiRK

Differential Revision: https://reviews.bitcoinabc.org/D16232