Documenting the behaviors of various config arguments in mlperf.conf and user.conf

[anandhu-eng]

It would be good to document the behaviors of various config arguments in mlperf.conf and user.conf like the min_query_count, max_duration, etc so that the questions like Would SingleStream performance run exit on attaining the minimum required duration even though the run executed only the fraction of generated_query_count raised in issue 2308 could be easily answered.

[tanvi-mlcommons]

Could go to Readme for testSettings.