Improve malware-scan output about wordfence-cli

[dallaskeene]

Verified the changes are working as expected including the following:

1. Check that malware-scan output now reads “Found [number] suspicious file(s) . . .”.
   Example message: Found 1 suspicious file(s) after processing 2300 file(s) containing 52.1 MiB over 109 second(s)
2. Check both, stdout and the curses interface using --progress
3. Check that malware-scan output now scales units based on value
4. Check that various values appear correctly, such as B, KiB, MiB, etc.
5. Additional testing completed that includes:
   • Check that --output-path still redirects and the output messaging still appears correctly when using this option.
   • Check output with a free key
   • Check output with a premium key