gh-93096: Move random benchmark into pyperformance - #131144

cc @vstinner
:-)

This isn't a performance test. It is used by module maintainers to view generated distributions to see if they match the expected distributions.

I think it would be right to get rid of the --test flags in modules with cli.
This flag is not documented and is not displayed in the --help output.

And it seems author of this flag is not against removing it

I'm going to decline this. It isn't part of the public API so there is no user benefit to removing it. I do use this when maintaining the module so it does have some value. And the test code has nothing to do with pyperformance so this PR would be moving the code from where a mainainer can find it to a place where it clearly doesn't make sense.