test: Set catch_system_errors=no on boost unit tests

Summary:
Boost does not handle asserts well in unit tests. Encountering one causes
test_bitcoin to hang indefinitely. This may explain the occassional timeouts we're
experiencing in CI.

See https://www.boost.org/doc/libs/1_68_0/libs/test/doc/html/boost_test/utf_reference/rt_param_reference/catch_system.html

Backport of Core PR18183

Test Plan:
Introduce assert(0); into a unit test, then: ninja check
Pre-patch, ninja check hangs until killed (Ctrl+C).
Post-patch, ninja check errors out as expected.

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D8014