Alternative definition layout of IArray

[nicolasstucki]

This PR changes the layout from

object opaques:
  opaque type IArray[+T] = Array[_ <: T]
  ... // extensions
end opaques

type IArray[+T] = opaques.IArray[T]

object IArray:
   ... // module methods
end IArray

to the following layout

package scala

opaque type IArray[+T] = Array[_ <: T]

object IArray:
  ... // extensions
  ... // module methods
end IArray

We lose the possibility of inlining the IArray.apply constructor methods. This PR handles those apply methods in the ArrayApply phase. This actually improved the bytecode generated.

This is a part of #11298

Migration

// IArray type
- scala.opaques.IArray
+ scala.IArray 

// extension methods: apply, length, take, ...
- scala.opaques.arrayOps.xyz
+ scala.IArray.xyz

[nicolasstucki]

Rebased - no conflicts