rgw/v2: improve logging to io_info.yaml and tests logs

[rakeshgm]

Logs are written to a file for every io operation and every io information is logged into a file. The io info file opens and closes for every io entry. So the tests executions take a lot of time when tests run for days as the log and io entry file size grows.
for example, consider a scenario where the io info file is greater than 3 GB as a result of tests running for over 5 days. now for every io entry, we are opening 3 GB file and closing. the performance of the tests executions takes a hit here. this becomes more problematic if the io size is small like around 1 MB. Writing 1 MB to cluster will be faster than writing the entry to the io log file - this will increase the test execution time and portray it as slow IO on the cluster.