Add override/final modifiers to V1TransportDeserializer
Summary:
Completes backport (7/7) of core PR16202:
https://github.com/bitcoin/bitcoin/pull/16202/commits/ed2dc5e48abed1cde6ab98025dc8212917d47d21
Depends on D8227.
Test Plan:
ninja all check-all
Reviewers: #bitcoin_abc, PiRK, jasonbcox
Reviewed By: #bitcoin_abc, PiRK, jasonbcox
Differential Revision: https://reviews.bitcoinabc.org/D8228