Refactor SinusoidalPositionEmbeddings class and update related methods for clarity and consistency

Fix bug in down sample

fix bug in time embedding

Fix assertions and tensor device handling in Sinusoidal_embedding class

Reintroduced beta scheduler

Remove unused beta parameters from model.py

changed batch size for loading

Add DDIM sampling function for image generation

Add EMA class for exponential moving average weights management

Full Unet class assembled with everything

Add downsample and upsample classes for improved model architecture

Resblock for the model

Add model and requirements for sinusoidal and time embeddings