Extract CSipHasher to it's own file in crypto/ directory.
This is a move-only commit with the exception of changes to includes.
backported from core PR14074 ( 4fb789e9b )
Test Plan: make check
Reviewers: #bitcoin_abc, deadalnix, jasonbcox
Reviewed By: #bitcoin_abc, deadalnix, jasonbcox
Subscribers: Fabien, jasonbcox
Maniphest Tasks: T589
Differential Revision: https://reviews.bitcoinabc.org/D2800