1 bit, ternary image generation support

**Is your feature request related to a problem? Please describe.**
Currently no support for 1 bit image generation

**Describe the solution you'd like.**
[1-bit and Ternary Bonsai Image 4B: Image Generation ](https://prismml.com/news/bonsai-image-4b)

**Describe alternatives you've considered.**
https://github.com/PrismML-Eng/Bonsai-image-demo

Start by reviewing the linked Bonsai Image 4B announcement and demo, then compare their 1-bit and ternary image-generation requirements with diffusers' existing support. Done should be defined as a supported generation path with coverage for both requested modes; the issue names no implementation files or tests.

Written by the indexing model from the issue text.