test: Add ASSERT_DEBUG_LOG to unit test framework

Summary:

• logging: Add member for arbitrary print callbacks
• test: Add ASSERT_DEBUG_LOG to unit test framework

This is a backport of Core PR16540

Test Plan:

make check

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D5909