Refine redundant null checks interpreter

The main change here is addition of a check that NotNullBasicValue instances
are not being created for non-reference types

Exactly this change should be used instead of f25f0db10e
The latter commit lead to problem described in the KT-14242 issue:
v.getType().getSort() == w.getType().getSort() && (v.getType().getSort() != Type.OBJECT || v.equals(w))

Problem is that the condition above returns true without calling `v.equals(w)`,
because the sort of type is ARRAY, not OBJECT, so testArray was being treated
as NotNullable erroneously

So the second part of this change is effectively revering mentioned commit

 #KT-14242 Fixed

compiler/testData/codegen/box/regressions/arrayLengthNPE.kt

@@ -0,0 +1,13 @@
+// See KT-14242
+var x = 1
+fun box(): String {
+    val testArray: Array<String?>? = when (1) {
+        x -> null
+        else -> arrayOfNulls<String>(0)
+    }
+
+    // Must not be NPE here
+    val size = testArray?.size
+
+    return size?.toString() ?: "OK"
+}