Value Types: Check the list of *.toArray() methods that can skip null check in storing into non-nullable arrays

[a7ehuo]

This issue is created to track a follow up work item related to #18464 (comment). A list of *.toArray() methods are disabled in canSkipNonNullableArrayNullStoreCheck[] since they explicitly store null into arrays. We need to check in the future after these methods are update if we can skip null check in storing into non-nullable arrays.

   // TR::java_util_EnumMap__nec_, // Disable it for now because EnumMap.toArray explicitly stores null into array element
   // TR::java_util_ArrayList_all, // Disable it for now because ArrayList.toArray explicitly stores null into array element
   // TR::java_util_concurrent_ConcurrentHashMap_all, // Disable it for now because ConcurrentHashMap.toArray explicitly stores null into array element
   // TR::java_util_Vector_all, // Disable it for now because Vector.toArray explicitly stores null into array element

   // The following list is identified after running sanity.functional tests
   // TR::java_util_AbstractCollection_all, // Disable it for now because AbstractCollection.toArray explicitly stores null into array element
   // TR::java_util_ArrayDeque_all, // Disable it for now because ArrayDeque.toArray explicitly stores null into array element
   // TR::java_util_IdentityHashMap_all, // Disable it for now because IdentityHashMap.toArray explicitly stores null into array element
   // TR::java_util_ImmutableCollections_all, // Disable it for now because ImmutableCollections.toArray explicitly stores null into array element
   // TR::java_util_LinkedList_all, // Disable it for now because LinkedList.toArray explicitly stores null into array element

[hzongaro]

We need to check in the future after these methods are update if we can skip null check in storing into non-nullable arrays.

Alternatively, if the store of a null reference is kept even when null-restricted arrays are supported, we might want to recognize those toArray methods, so that all other methods in those classes can fall under the _all enumerated value, and be recognized as not requiring checks for stores of null references to null-restricted arrays.