remove walletmodel circular dependency

Summary:
This is part 2 of 4 of the backport of Core PR17513.

It includes commits a53e989 and 567cb44.

Additional changes were necessary on our side to remove the circular dependency because of codebase divergence related to BIP70 support. The PaymentServer::fetchPaymentACK method was changed to use a interfaces::Wallet& instead of a WalletModel*.

Depends on D7572

Test Plan: ninja && ninja check

Reviewers: O1 Bitcoin ABC, #bitcoin_abc, deadalnix, Fabien

Reviewed By: O1 Bitcoin ABC, #bitcoin_abc, deadalnix, Fabien

Subscribers: Fabien, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D7602