Increase default repetitions during codspeed walltime runs, and fix walltime stats computation#34

GuillaumeLagrange merged 4 commits intomainCodSpeedHQ/codspeed-cpp:mainfrom

cod-1639-fix-codspeed-cpp-walltimetotaltime-and-maybeCodSpeedHQ/codspeed-cpp:cod-1639-fix-codspeed-cpp-walltimetotaltime-and-maybeCopy head branch name to clipboard