Use weighted apdex scoring

Using weighted apdex scores means that components with very low RPS values won't have an outsized impact on the Apdex score.

This doesn't happen for the web apdex, which is measured with a single component (workhorse) but it happens with Sidekiq.

In sidekiq, the pages priority only receives a few requests a second. Therefore a single slow request could bring the pages component apdex down to 50%. This has an outsided impact on the apdex of the entire sidekiq service. It shouldn't.

This change uses a weighted average. The weight is based on the RPS of the component. This means that each components impact will be determined by the number of requests it receives, instead of the inverse.

This is how the weighted and non-weighted apdex scores for Sidekiq compare. The weighted averages have far fewer drops.