Improve benchmark comparison printout ("slower"->"faster") (#53221)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/53221

# Changelog:
[Internal] -

This changes the benchmark test results comparison print the results slightly differently, in particular it now uses the slowest result as a baseline and prints how much faster the other ones are (as opposed to printing "slower" previously).

This arguably brings a more positive vibe when looking into the benchmark results :)

Reviewed By: andrewdacenko

Differential Revision: D80082134

fbshipit-source-id: 7dc9c7c520afe08270d4f5da9031db02261690ba