[avalanche] Add preconsensus validation callbacks

Summary:
This will be used to bind chronik to the preconsensus events.
Note that the invalidation callback will be called directly in net_processing in a later diff because there is no way to test it yet otherwise.

Depends on D18407.

Test Plan:

ninja all check-all

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D18411