test: rename CTransaction .sha256 -> .txid_int for consistency
Summary:
Note that we unfortunately can't use a scripted diff here, as the same
property name is also used for CBlockHeader/CBlock instances.
This is a partial backport of core#32421
https://github.com/bitcoin/bitcoin/pull/32421/commits/81af4334e8f903601dac503426eaccc1d3527f9c
Depends on D18714
Test Plan: ninja check-functional-extended
Reviewers: #bitcoin_abc, Fabien
Reviewed By: #bitcoin_abc, Fabien
Differential Revision: https://reviews.bitcoinabc.org/D18715