[avalanche] Add a facility to update node's timeout

Summary:
This feature is required as any reply from the node comes with a cooldown time.

Depends on D6824

Test Plan:

ninja all check-avalanche

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D6825