stable diffusion adapter pipeline for t2i adapter missing `from_single_file`

**Is your feature request related to a problem? Please describe.**
I want to use and test out the t2i adapter with my safetensor model. I used to use diffusers models, but none work since the update. Many of the other adapters use `from_single_file` to load safetensors correctly. I keep bringing this up, but the current design on having multiple ways to load files is terrible since many adapters seem to not inherit loading methods.

**Describe the solution you'd like.**
To be able to load safetensors files from a local directory with the stable diffusion adapter pipeline for t2i. from_single_file is missing and it's annoying that from_pretrained can't do it either.

**Describe alternatives you've considered.**
Automatic1111, I just want to test with a specific model. I don't have time to waste on other models.

**Additional context.**
I keep saying this over and over, but making all the loading methods load both safetensors and diffusers.