OctreeHelper: Add update().

[erasta]

Related issue: #23481

When Octree changes, you need to recreate another OctreeHelper. This PR adds an update() method to rebuild the visualization on the same geometry.

[WestLangley]

The update() method is calling dispose() in this PR.

TBH, I'm thinking that adding a dispose() method would be more appropriate than adding an update() method here.

This class can't be simply updated -- a new instance is generally required.

It is the app's responsibility to call dispose() when appropriate.

At least, that has been our policy.

Without a consistently-implemented policy, users will never know when calling dispose() is required at the app level.

[Mugen87]

This class can't be simply updated -- a new instance is generally required.

I've also thought about this although other helpers do have update methods. I'm okay for both approaches in context of OctreeHelper.

[erasta]

The update() method is calling dispose() in this PR.
TBH, I'm thinking that adding a dispose() method would be more appropriate than adding an update() method here.
This class can't be simply updated -- a new instance is generally required.
It is the app's responsibility to call dispose() when appropriate.
At least, that has been our policy.
Without a consistently-implemented policy, users will never know when calling dispose() is required at the app level.

Some helpers have a dispose(), more helpers have an update() method, and others have some variant of it as ArrowHelper.SetDirection().
I agree with you that there should be a dispose() method, and more than that:
All helpers should implement both dispose() and update() methods, either with regulation on code reviews, or by enforcing it using some mechanism such as base class.
(However, in this PR i didn't want to rock the boat)

[Mugen87]

I don't think that something like AxesHelper needs an update() method.

[WestLangley]

This class can't be simply updated -- a new instance is generally required.

I've also thought about this although other helpers do have update methods.

But the update methods just update the buffer data.

In this case, I think an update() method is unwise, for the reasons I stated above.

I would prefer to see a dispose() method added, instead.

[erasta]

Added dispose() method that also disposes of the material, as other helpers do.
Kept the update() method, because sometimes it's beneficial to retain the object reference instead of disposing and recreating it. Hope this is ok with you.
There's a recursion there that i want to change into a loop, but not sure if this is for separate PR.
Thank you.