Some projects need more than 8-bit RGBA off-screen, so add the ability to
accept color format and defaults to RGBA8 so existing code should not be
affected.
Currently supported formats:
- RGBA8 (default)
- RGBA16
- RGBA16F
- RGBA32F
Reviewed By: mano-wii
Differential Revision: https://developer.blender.org/D13650