scripted-diff: rename TxRelay & TxProof members

Summary:
This concludes backport of core#21160
https://github.com/bitcoin/bitcoin/pull/21160/commits/1066d10f71e6800c78012d789ff6ae19df0243fe

Depends on D14710

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D14711