Scala 3: work around FactoryConstructor failing with polymorphic @With annotation in one most common case

[neko-kai]

We're working around scala/scala3#16468 only in case where type variable is present both in With-annotation and on the annotated type:

trait XCarrier[T] {
  def x: Option[T] @With[Some[T]]
}

If the type variable is not present on the annotated type, we'll still fail as before:

trait XCarrier[T] {
  def x: Any @With[Some[T]] // can't figure out that T is XCarrier.T without the left-hand side mentioning T
}

[codecov-commenter]

Codecov Report

Merging #1943 (5b595fb) into develop (b18cb1c) will decrease coverage by 0.21%.
The diff coverage is n/a.

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@@             Coverage Diff             @@
##           develop    #1943      +/-   ##
===========================================
- Coverage    64.56%   64.36%   -0.21%     
===========================================
  Files          545      545              
  Lines        10939    10939              
===========================================
- Hits          7063     7041      -22     
- Misses        3876     3898      +22