Merge branch 'network-assets' into 'master'

Replace raphael-rails with raphael.js and split it from the rest of the JS

## What does this MR do?

Removes raphael.js and its related libraries from the default JS bundle.

It also removes raphael-rails because the gem is unmaintained and – for whatever reason – didn't want to cooperate with the way I was trying to require it.

This brings the default (compressed and minified) application.js from 354KB after the d3 MR (!4394) down to 324KB.

## Are there points in the code the reviewer needs to double check?

That tests pass and that there aren't errors on any pages (especially the Network page).

## Why was this MR needed?

It's only used on the Network page and was using way too much bandwidth for just one page.

## What are the relevant issue numbers?

#14372 #13165 

Follow-up to !4394 and !4516.

cc: @jschatz1 

See merge request !4519