test: Bump timeouts to accomodate really slow disks

Summary: Backport of core PR18249.

Test Plan:

./test/functional/test_runner.py feature_block

ninja bitcoin-fuzzers
./test/fuzz/test_runner.py <path_to_corpus>

Reviewers: #bitcoin_abc, PiRK

Reviewed By: PiRK

Differential Revision: https://reviews.bitcoinabc.org/D8230