Interface SceneTreesUpdateOptions

Timestamps around everything the update records into the encoder (tree copies, quantize and identity passes, refits, growth copies, the top level): beginningOfPassWriteIndex is written by a tiny compute pass before the update's first command, endOfPassWriteIndex by one after its last (each only when given). The caller resolves the query set. Not in the bracket: GPU builds and capped batches' copies, which go in submits of their own (timestamps times the builds).