Log: Include <fmt/core.h> instead <fmt/format.h>.
Log: Include <fmt/core.h> instead <fmt/format.h>.

Use the lighter weight <fmt/core.h> header in <marc/Log.h> instead of
<fmt/format.h>.  MaRC's logging functions currently only use the core
functionality of the fmt library.

ossama-othman/MaRC,ossama-othman/MaRC,ossama-othman/MaRC