This method uses Gitlab::Profiler::TotalTimeFlatPrinter internally, which is the
same as RubyProf::FlatPrinter, but the min_percent option (and new max_percent
option) applies to the _total_ time, not the _self_ time. This helps us figure
out if we're calling a library inefficiently, for instance.

This method makes it easier for other parts of the app to get clean backtraces,
as well as console users.

Gitlab::Profiler.profile takes a URL to profile, and returns the ruby-prof
profile result.

This is currently only for interactive use (in a console) or from the script
runner. Note that when using this interactively, changes to the application
within that console session will be used, so this can be used to test proposed
performance changes.