Function effective_usage 

pub fn effective_usage(
    usage: TextureUsages,
    transient_saves_memory: bool,
) -> TextureUsages

The usage a pooled texture requested as usage is actually created with.

Adds wgpu::TextureUsages::TRANSIENT_ATTACHMENT — which lets a driver keep the texture in tile memory and possibly never back it with real storage — on an adapter that reports it saves memory, and only for a texture whose entire usage set is RENDER_ATTACHMENT. That restriction is wgpu’s own: TRANSIENT_ATTACHMENT requires RENDER_ATTACHMENT and is incompatible with every other usage, which lines up exactly with “an intermediate nothing reads back”. Anything sampled, copied or stored keeps its usage unchanged and relies on the clear/discard ops alone.