Consider changing logger implementation

[makaimann]

A few reasons to change the logger implementation:

• it seems like the logger evaluates all the arguments regardless of the verbosity (e.g. even if it doesn't print it). This means the to_string for large terms could be called all the time even at low verbosity.
• I believe it is the only part of the codebase that uses C++17

Could consider looking into a stream based one -- maybe that would help. A macro could also work, but we do want to be able to change the verbosity dynamically so it would have to take an argument.