Move ::nMaxTipAge into ChainstateManager

Summary:
This is a partial backport of core#25704 and core#26477
https://github.com/bitcoin/bitcoin/pull/25704/commits/faf44876db555f7488c8df96db9fa88b793f897c
https://github.com/bitcoin/bitcoin/pull/26477/commits/a451e832b46bcb984dfcd9478ea8ebb8b3de0c62

Depends on D15809

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D15811