test: bump timeouts for feature_block and feature_abortnode

Summary:
I recently saw feature_abortnode fail to start due to a rpc timeout.

This is a partial backport of core#18392
https://github.com/bitcoin/bitcoin/pull/18392/commits/fa92af5af39a08982f785542df5419d6d5a4706d

Test Plan: ninja check-functional

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D12635