Test util_backtrace

What is the new feature

Add simple test for util_backtrace, use ctest insteas of make test to have instant message about failing tests

How is it implemented

Capture stdout in a buffer, then check if buffer contains certain key substrings

Mandatory steps before review

• Gitlab CI passes (Hint: use make format for linting)
• New feature is covered by additional unit tests
• Mark the merge request as ready by removing Draft:

Mandatory steps before merge

• Reviewed by a maintainer
• Incorporate review suggestions

You are not supposed to merge this request by yourself, the maintainers of fortan-support take care of this action!