refactor: shift CopyrightHolders() and LicenseInfo() to clientversion.cpp

Summary:
This is a partial backport of core#24409
https://github.com/bitcoin/bitcoin/pull/24409/commits/4c3e3c57463b029d335e685d3dcdaf26456666cf

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D16215