OBJ, PLY, and STL used a mix of fprintf, std::cout, and std::cerr to
trace warnings, errors, and general messages to the console.
Now, we instead use CLOG which provides real facilities for warnings and
errors and generally removes the need to pull in and use the heavy
`<iostream>` machinery.
For traces that should always be printed, `fmt::print` is used since
CLOG currently doesn't provide that particular level of trace.
Tests were only minimally changed to drop usage of streams while keeping
their prior usage of older stdio APIs. We can change to using fmtlib
there too if desired.
Pull Request: https://projects.blender.org/blender/blender/pulls/130107
c9c2fbc52d