tests: Avoid hitting some known minor tinyformat issues when fuzzing strprintf(...)
Summary:
Avoid hitting some known minor tinyformat issues when fuzzing strprintf(...). These can be removed when the issues have been resolved upstreams :) Note to reviewers: The %c and %* issues are also present for %<some junk>c and %<some junk>*. That is why simply matching on "%c" or "%*" is not enough. Note that the intentionally trivial skipping logic overshoots somewhat (c[…]% is filtered in addition to %[…]c).
Backport of core PR18109.
Test Plan:
ninja bitcoin-fuzzers ./test/fuzz/test_runner.py <path_to_corpus>
Reviewers: #bitcoin_abc, PiRK
Reviewed By: #bitcoin_abc, PiRK
Differential Revision: https://reviews.bitcoinabc.org/D8957