rspq: support enqueuing commands into different one-time lists #781
Description
The usecase is for being able to draw to different "layers" in a game (e.g. opaque, transparent) without having to loop over everything multiple times. So simply submit the parts of models into different queues so to speak.
One possible solution is to allow to record multiple blocks at the same time, where the blocks are effectively one-time use and only serve as a means to have different queues. One option for this, API-wise would be to allow "continuing" a block after finishing it, though this would currently be O(n) as we don't store the "end" pointer in the block itself (though we could start).
Another solution is to somehow have multiple "lowpri" queues, though it's not clear how that'd work. On the CPU side, you can have an API to switch current lowpri, but on the RSP this would require more code to be added, which is probably not worth doing.