improvement: model training and model inference pages

For Model Inference specifically:

• There shouldn't be a label path field

For both Model Training and Model Inference pages:

• Shouldn't be able to click "Start training" (or "Start inference") without filling in all mandatory fields
• "Set inputs" and "Base configuration" (where user uploads yaml file) can be included on just one page
• Since we're assuming our end-users don't code, they likely won't be doing any additional configuring after uploading a yaml file, so the "Advanced configuration" option should be a more hidden, clearly optional step before starting training or inference