Introduce Logger class with tests

[PhilipFackler]

Description

This introduces a logging tool so that we can move away from using std::cout/std::cerr directly.

Closes #270
Closes #129

Proposed changes

The new class and its tests were lifted directly from Re::Solve, see here and here.

Checklist

• All tests pass.
• Code compiles cleanly with flags -Wall -Wpedantic -Wconversion -Wextra.
• The new code follows GridKit™ style guidelines.
• There are unit tests for the new code.
• The new code is documented.
• The feature branch is rebased with respect to the target branch.
• I have updated CHANGELOG.md to reflect the changes in this PR. If this is a minor PR that is part of a larger fix already included in the file, state so.

[nkoukpaizan]

This works. I have a few suggestions on the target name choices, consolidating some definitions and namespaces.