Currently in mozperftest we have this install_package function, and it's unclear why we needed it in the first place. We should see if we can find a standard way of installing these packages as the current method is highly prone to causing failures like bug 1849610. I think it might be related to the push-to-try feature we have in mozperftest, but we plan on removing that in favour of mach try perf. That said, it's possible that we need to do it this way because we're not using mozharness in mozperftest, and are actively avoiding it.