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/inference/nullability/arrayOfArraysOfNull.kt

@@ -0,0 +1,10 @@
+class Test {
+    fun foo() {
+        val ss = Array</*T2@*/Array</*T1@*/String?>>(5/*LIT*/, { arrayOfNulls</*T0@*/String?>(5/*LIT*/)/*Array<T0@String!!U>!!L*/ }/*Function0<Int, T3@Array<T4@String>>!!L*/)
+    }
+}
+
+//T4 := UPPER due to 'RETURN'
+//LOWER <: T3 due to 'RETURN'
+//T1 := T4 due to 'PARAMETER'
+//T3 <: T2 due to 'PARAMETER'