clear and preload function for useEnvironment

[AaronClaes]

Describe the feature you'd like:

Since useEnvironment is based on useLoader it should be possible to provide a preload and clearing function.
At the moment, it would be quite a bit of trouble to preload or clear environment files because some logic is involved in selecting the correct loader based on the file extension.

Suggested implementation:

Similar to the other hooks based on useLoader:

useEnvironment.clear(...)
useEnvironment.preload(...)

I worked out a first version in a Drei fork and it works great so far, I will open a PR soon.
The only limitation at the moment would be that you cannot preload gainmaps, because that loader requires the renderer to be set.
This should not be an issue as long as it is documented.

[github-actions]

🎉 This issue has been resolved in version 9.112.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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