[UUM-137284] Fixing warnings of 6.4+ due to obsoleted APIs

[LeoUnity]

Purpose of this PR

Ticket/Jira #: UUM-137284

Fixing 2 warnings:

``(...)\com.unity.formats.fbx\com.unity.formats.fbx\Editor\ConvertToNestedPrefab.cs(277,30): warning CS0618: 'EntityId.GetRawData()' is obsolete: 'Please use EntityId.ToULong(EntityId) instead.'```

``(...)\com.unity.formats.fbx\com.unity.formats.fbx\Editor\ConvertToNestedPrefab.cs(286,29): warning CS0618: 'SearchService.GetItems(SearchContext, SearchFlags)' is obsolete: 'GetItems is deprecated, please use Request instead. GetItems will be removed in a future version.'````

Testing

Functional Testing status:

Performance Testing status:

Documentation & UX Writing

User facing text to review		Details
User interface
Public API docs
Changelog

Documentation halo effect		Jira link
User manual
Other docs

Additional information

Note to reviewers:

Reminder:

• Rebase on Update Wrench to 2.3.1 #749 and push for CI before merging this PR

[u-pr]

The review has identified several issues in ConvertToNestedPrefab.cs, including potential compilation errors on older Unity versions, null safety concerns, and performance implications of synchronous search operations. Summary of new findings:

• High Importance: Potential compilation errors related to EntityId.ToULong usage and ISearchList return types.
• Medium Importance: Risk of NullReferenceException when resolving search results.
• Low Importance: Use of synchronous search requests may impact Editor performance.

_{🤖 Helpful? 👍/👎}

[u-pr]

Using SearchFlags.Synchronous and creating a new SearchContext (line 283) inside this method can significantly impact performance and lead to UI freezes in the Editor, especially in large projects. If GetSceneReferences is called frequently (e.g., in a loop over many objects), consider reusing the SearchContext or using an asynchronous search request with a callback.

_{🤖 Helpful? 👍/👎}

[u-pr]

Have you considered that x.ToObject() might return null if the search result cannot be resolved to a valid UnityEngine.Object (e.g., if the object was destroyed or is in an unloaded scene)? To improve robustness, you might want to filter out these null values before returning the list to avoid potential NullReferenceExceptions in the caller. For example:

return items.Select(x => x.ToObject()).Where(obj => obj != null).ToList();

_{🤖 Helpful? 👍/👎}