Switch all callers from poly1305_auth to Poly1305 class

Summary:
This also removes the old poly1305_auth interface, as it no longer serves any
function. The new Poly1305 class based interface is more modern and safe.

This concludes backport of core#27993
https://github.com/bitcoin/bitcoin/pull/27993/commits/4e5c933f6a40c07d1c68115f7979b89a5b2ba580

Depends on D19015

Test Plan: ninja all check-all bench-bitcoin bitcoin-fuzzers

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D19016