addGlobalImport should group imports by ref

[olafurpg]

Currently it produces output like this

import scala.Predef.{ augmentString => _ }
import scala.Predef.{ intArrayOps => _ }
import scala.`package`.{ List => _ }
import scala.`package`.{ Vector => _ }
import scala.Predef.{ Map => _ }
import scala.`package`.{ :: => _ }
import scala.`package`.{ Seq => _ }
import scala.`package`.{ #:: => _ }
import strawman.collection.immutable.HashMap
import strawman.collection.immutable.Vector
import strawman.collection.immutable.Map
import strawman.collection.immutable.Nl
import strawman.collection.immutable.List
import strawman.collection.immutable.LazyList
import strawman.collection.mutable.ArrayBuffer

it would be nice if it grouped by shared prefix.

[gabro]

Is this the same as #199?

[olafurpg]

Close but there's a minor difference, those imports are inserted by scalafix with the ctx.addGlobalImport patch. If I understand correctly, the other rewrite is about grouping existing imports together which is a bit harder.