[refactor] Drop unused state.DoS(), state.GetDoS(), state.CorruptionPossible()

Summary:
Co-authored-by: Anthony Towns <aj@erisian.com.au>

This is a partial backport of Core PR15141 : https://github.com/bitcoin/bitcoin/pull/15141/commits/12dbdd7a41bac73e51ed8f7b290b7671196bf9ea

Depends on D6734 and D6736

Test Plan:

ninja all check-all

Reviewers: #bitcoin_abc, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Differential Revision: https://reviews.bitcoinabc.org/D6737