Rename or merge GHC.JS.{Core,STG,}Utils
One thing I often do to open GHC.Core.Utils is to type CoreUtils
into my fuzzy file finder.
This became a lot more tedious since we merged the JS backend, because now the first match is GHC.JS.CoreUtils
.
It is similar for GHC.Stg.Utils, but I don't search for it that often.
Hence I propose to merge those modules into a single GHC.JS.Utils
module. They aren't that big to begin with (perhaps 600 lines after the merge).