p2p: Integrate DumpAnchors() and ReadAnchors() into CConnman

Summary:
This is a backport of core#17428 [4/7]
https://github.com/bitcoin/bitcoin/pull/17428/commits/4170b46544231e7cf1d64ac3baa314083be37502

Depends on D10509

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, majcosta

Reviewed By: #bitcoin_abc, majcosta

Subscribers: majcosta

Differential Revision: https://reviews.bitcoinabc.org/D10510