v0.15.1: Patch Release to fix safety checker, config access and uneven scheduler

Fixes bugs related to missing global pooling in controlnet, img2img processor issue with safety checker, uneven timesteps and better config deprecation

• [Bug fix] Add global pooling to controlnet by @patrickvonplaten in #3121
• [Bug fix] Fix img2img processor with safety checker by @patrickvonplaten in #3127
• [Bug fix] Make sure correct timesteps are chosen for img2img by @patrickvonplaten in #3128
• [Bug fix] Fix config deprecation by @patrickvonplaten in #3129