Fix incorrect self type of closures

[WojciechMazur]

This PR fixes #2552 and its reachability errors. The problem with the mentioned issue was caused by usage of incorrect self type for the object containing closure ( SN synthetic Lambda class) and was partially introduced due to changes of how symbols ownership is perceived in Scala 3 or due to the fact that genNir phase is executed after flatten scalac phase.
When generating the closure symbol of the current class saved in curClassSym in the outer scope of AST traversal was different the owner of function passed to the Closure.

object example {
  val foo = () => println("foo") // curClassSym = `example$`; closure.fun.owner = `example$` 
  object inner {
    val foo = () => println("inner foo") // curClassSym = `example$`; closure.fun.owner = `example$foo$`
  }
}

We cannot change the naming of the Scala Native synthetic Lambda class at this point because it might lead to binary incompatibility with 0.4.3 release. Luckily, this is not needed. Reachability errors that we could have observed were caused by method dispatch which was using incorrect self type. Using closure.fun.owner for self type instead of curClassStm fixes the problem.

• Added reproducer tests for issue 2552
• Changed self type used for closure inner structure

Additional fix:

• I've observed warning when compiling scalalib, removing tail whitespace from patches fixed that issue