New J2K: separate nullability inference from common one & nullability bug fixes

It will be needed for structure mutability inference

#KT-21467 fixed
#KT-32609 fixed
#KT-32572 fixed
#KT-24677 fixed

nj2k/testData/newJ2k/function/externalKtFunctionalInterface.kt

@@ -11,6 +11,6 @@ internal class Test {
     fun nya(): Double {
         //TODO explicitlly call apply here
 
-        return foo(1, FunctionalI<Int, Double> { x: Int -> this.toDouble(x) })
+        return foo(1, FunctionalI<Int?, Double?> { x: Int -> this.toDouble(x) })
     }
 }

nj2k/testData/newJ2k/function/internalFunctionalInterface.kt

@@ -1,4 +1,3 @@
-// ERROR: Type mismatch: inferred type is B? but B was expected
 // ERROR: Unresolved reference: A
 // ERROR: Interface FunctionalI does not have constructors
 internal interface FunctionalI<A, B> {
@@ -6,7 +5,7 @@ internal interface FunctionalI<A, B> {
 }
 
 internal class Test {
-    fun <A, B> foo(value: A, `fun`: FunctionalI<A?, B?>): B {
+    fun <A, B> foo(value: A, `fun`: FunctionalI<A, B>): B {
         return `fun`.apply(value)
     }
 
@@ -15,6 +14,6 @@ internal class Test {
     }
 
     fun nya(): Double {
-        return foo(1, FunctionalI<Int, Double> { x: A -> this.toDouble(x) })
+        return foo(1, FunctionalI<Int?, Double?> { x: A -> this.toDouble(x) })
     }
 }

nj2k/testData/newJ2k/function/ownGenericParam.kt

@@ -1 +1 @@
-fun <U> putU(u: U?) {}
+fun <U> putU(u: U) {}

nj2k/testData/newJ2k/function/ownSeveralGenericParams.kt

@@ -1 +1 @@
-fun <U, V, W> putUVW(u: U?, v: V?, w: W?) {}
+fun <U, V, W> putUVW(u: U, v: V, w: W) {}