[K/N] Make classes generated from λs that use generic parameters generic

Previously, a function reference that used generic parameters from its
outer scope was lowered into a top-level non-generic subclass of
`FunctionN`, with `FunctionN` type arguments referencing type parameters
not present in the scope anymore. This sometimes resulted in generating
malformed mangled names.

From now on the generated subclass of `FunctionN` is generic. The needed
type arguments are passed upon instantiation, when the relevant generic
parameters are present in the scope.

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/util/IrTypeParameterRemapper.kt

@@ -13,11 +13,12 @@ import org.jetbrains.kotlin.ir.types.impl.IrSimpleTypeImpl
 import org.jetbrains.kotlin.ir.types.impl.IrTypeAbbreviationImpl
 import org.jetbrains.kotlin.ir.types.impl.makeTypeProjection
 
-/* After moving an IrElement, some type parameter references within it may become out of scope.
-   This remapper restores validity by redirecting those references to new type parameters.
+/**
+ * After moving an [org.jetbrains.kotlin.ir.IrElement], some type parameter references within it may become out of scope.
+ * This remapper restores validity by redirecting those references to new type parameters.
  */
 class IrTypeParameterRemapper(
-    val typeParameterMap: Map<IrTypeParameter, IrTypeParameter>
+    private val typeParameterMap: Map<IrTypeParameter, IrTypeParameter>
 ) : TypeRemapper {
     override fun enterScope(irTypeParametersContainer: IrTypeParametersContainer) {}
     override fun leaveScope() {}
@@ -56,4 +57,4 @@ class IrTypeParameterRemapper(
         ).apply {
             annotations.forEach { it.remapTypes(this@IrTypeParameterRemapper) }
         }
-}
+}