Added support for parallel Snap3D Generations

[jbienzss]

This PR resolves #8 and enables multiple Snap3D generations at the same time.

The only blocker was reusing the same material across instances of Snap3DInteractable prefab. The simple fix was to clone the material before assigning the image. Then simply remove the bool check of availableToRequest in Snap3DInteractableFactory.

[skang2-sc]

In this particular example, which is also included with Lens Studio, we deliberately set the project up to wait for each generation to finish before starting the next. This helps prevent unintentional spamming for various reasons.

Please consider adding an option which enables this behavior while keeping the old behavior as the default.

[jbienzss]

If the design is intentional and you do not wish to allow more than one generation, I'm not sure it makes sense to circumvent that? In that case, might I suggest that you disable the microphone button and / or add a message when the user tries to submit more than one at a time?

Please be aware that if the user has a generation started from the Snap3D panel and also asks the Agent to generate a 3D object, the agent will say "I've started creating it" and nothing will appear.

[skang2-sc]

We do support multiple generations at the same time, but we want this to be a more intentional action rather than something enabled by default.

Please be aware that if the user has a generation started from the Snap3D panel and also asks the Agent to generate a 3D object, the agent will say "I've started creating it" and nothing will appear.

Hmmm shouldn't be the case, these are using two separate services, but will look into it. Thanks for flagging.