For the "Divide" layer blend mode to work in the viewport, we need to use
a floating point texture format for rendering.
This changes the format to always use floats for the `color` textures,
but still switches the `reveal_tx` to use integers in the viewport, and
only floating point during final render.
Pull Request: https://projects.blender.org/blender/blender/pulls/143993
00a979f2aa