get config via chainstatemanager when possible (2/n)

Summary:
In this diff we remove the unused config parameter from UnwindBlock and its callers.

Depends on D15796

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D15797