New J2K: implement mutability inference in post-processing

#KT-24293 fixed
#KT-19603 fixed

nj2k/testData/newJ2k/issues/kt-15791.kt

@@ -3,6 +3,6 @@ import java.util.ArrayList
 internal object A {
     @JvmStatic
     fun main(args: Array<String>) {
-        List::class.java.isAssignableFrom(ArrayList::class.java)
+        MutableList::class.java.isAssignableFrom(ArrayList::class.java)
     }
 }

nj2k/testData/newJ2k/issues/kt-5294.kt

@@ -1,4 +1,5 @@
-internal class X(private val list: MutableList<Y>) {
+internal class X(private val list: List<Y>) {
 
     internal inner class Y
+
 }