[SIP-71] `into[A]` type wrapper lost in mirror generation

[prolativ]

Compiler version

3.7.3-RC1-bin-20250619-b1da8fc-NIGHTLY

Minimized code

import scala.language.experimental.into
import Conversion.into

import scala.deriving.Mirror

object Opaques:
  opaque into type MyInto[+A] >: A = A

import Opaques.MyInto

case class Foo(x: Int)
case class Bar(foo: into[Foo])
case class Baz(foo: MyInto[Foo])

given Conversion[Int, Foo] = Foo(_)

def test = 
  val barMirror = summon[Mirror.Of[Bar]]
  summon[barMirror.MirroredElemTypes =:= (into[Foo] *: EmptyTuple.type)] // Doesn't compile unexpectedly
  summon[barMirror.MirroredElemTypes =:= (Foo *: EmptyTuple.type)] // Compiles unexpectedly

  val bazMirror = summon[Mirror.Of[Baz]]
  summon[bazMirror.MirroredElemTypes =:= (MyInto[Foo] *: EmptyTuple.type)] // Compiles as expected
  summon[bazMirror.MirroredElemTypes =:= (Foo *: EmptyTuple.type)] // Doesn't compile as expected

Expectation

into type should be preserved in mirror generation