[backport#16227 5/8] Move KeyOriginInfo to its own header file

Summary:
https://github.com/bitcoin/bitcoin/pull/16227/commits/16f8096e911e4d59292240a17e2d4004f0500b9e

Depends on D6556

Partial backport of Core PR16227

Test Plan:

ninja check

Reviewers: #bitcoin_abc, nakihito

Reviewed By: nakihito

Differential Revision: https://reviews.bitcoinabc.org/D6557