fuzz: Avoid running over all inputs after merging them
Summary:
This cuts the time it takes to merge inputs by half
Backport of core PR18509.
Depends on D8271.
Test Plan:
ninja bitcoin-fuzzers ./test/fuzz/test_runner.py <path_to_corpus> git clone https://github.com/Bitcoin-ABC/qa-assets.git ~/seeds ./test/fuzz/test_runner.py ~/seeds/fuzz_seed_corpus \ --m_dir=<path_to_corpus> \ -l DEBUG
Reviewers: #bitcoin_abc, PiRK
Reviewed By: PiRK
Subscribers: PiRK
Differential Revision: https://reviews.bitcoinabc.org/D8272