Box primitive types in position of generic receiver

#KT-9469 fixed

compiler/testData/codegen/box/extensionProperties/genericValMultipleUpperBounds.kt

@@ -0,0 +1,8 @@
+val <T> T.valProp: T where T : Number, T : Int
+    get() = this
+
+fun box(): String {
+    0.valProp
+
+    return "OK"
+}