[CMAKE] Increase the unit test verbosity to test_suite

Summary:
Default is error, this bumps to test_suite:
https://www.boost.org/doc/libs/1_64_0/libs/test/doc/html/boost_test/utf_reference/rt_param_reference/log_level.html

Test Plan:

ninja check

Cause a failure in a unit test and check the output is more verbose.

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D5882