Function createTextureRenderTarget

Wrap one layer and mip level of an existing renderable texture as a RenderTarget, so a frame-graph task (a render-draw task, an effect task, a clear) can draw into it: a tile slot of a texture array, a mip of a pyramid, or a plain render texture of any size and format.

The target holds one reference on the texture (released by disposeRenderTarget) and owns no attachment: disposing it never destroys the texture another owner still uses. One target per subresource is created once and reused; switching a task between targets of the same format allocates nothing.