chore: Replace IsSceneObject with InScenePlaced bool

[EmandM]

Purpose of this PR

Replace the bool? IsSceneObject that was calculated at runtime with a bool InScenePlaced field that's calculated in the asset post processor and a build system callback.

Jira ticket

n/a

Changelog

• Added: NetworkObject.InScenePlaced boolean for checking if an object is InScenePlaced.
• Deprecated: NetworkObject.IsSceneObject nullable boolean.

Deprecated API

• An [Obsolete] attribute was added along with a (RemovedAfter yyyy-mm-dd) entry.
• An api updater was added.
• Deprecation of the API is explained in the CHANGELOG.
• The users can understand why this API was removed and what they should use instead.

Documentation

• No documentation changes or additions were necessary.
• Includes documentation for previously-undocumented public API entry points.
• Includes edits to existing public API documentation.

Testing & QA (How your changes can be verified during release Playtest)

Functional Testing

Manual testing :

• Manual testing done

Automated tests:

• Covered by existing automated tests
• Covered by new automated tests

Does the change require QA team to:

• Review automated tests?
• Execute manual tests?
• Provide feedback about the PR?

If any boxes above are checked the QA team will be automatically added as a PR reviewer.

Backports

n/a