Fix: print diagnostics to stdout in s2n_resume_test

[ravindran-dev]

refs: #4112

Problem:

• Diagnostic messages in s2n_resume_test were printed to stderr.
• CTest doesn’t surface stderr reliably even with --output-on-failure, so these hints were invisible when the test fails.

Change:

• Replaced fprintf(stderr, ...) with printf(...) in s2n_resume_test so the diagnostic messages go to stdout and are visible in CTest output.

Testing:

Build:

cd /home/ravi/s2n-tls                                                                                                                                                                                          
rm -rf build
mkdir build
cd build

cmake .. -DCMAKE_BUILD_TYPE=Debug
cmake --build . -j8

Test:

ctest -R s2n_resume_test --output-on-failure

Output: