Clarify `useRenderPipeline` names

useRenderPipeline allows the user to store generic Three Node in a local store that is accessed via a property named passes. I had thought that this should then be typed as a record of PassNode but it turns out in practice it is not used this way, see: WebGPUMotionBlur example.

Is passes the correct name here?

Another suggestion is to rename scenePass to just scene since it is accessed from the passes key anyways and other additions to the record do not follow the *Pass naming convention.

passes.scene.setMRT()

// Instead of passes.scenePass.setMRT()