[Mitra] Add Intcode integer format

Summary:
Intcode integer format for a new transaction version.

Spec and rationale (including discussions on this topic) can be be found here.

Test Plan: ninja test_bitcoin && ./src/test/test_bitcoin -t serialize_intcode_tests

Reviewers: deadalnix, Fabien, #bitcoin_abc, roqqit

Reviewed By: deadalnix, Fabien, #bitcoin_abc, roqqit

Subscribers: roqqit, 0xGoerliMainnet

Differential Revision: https://reviews.bitcoinabc.org/D13101