Modular guiders should provide sane defaults

[vladmandic]

Modular guiders are a great concept, but right now they are nearly impossible to use due to sane lack of default values.
For example, PerturbedAttentionGuidance requires either SkipLayerGuidance: List[int] param or perturbed_guidance_config: LayerSkipConfig param

There are no chance that normal user would know any of such deep internals. Ask is to provide default values and any such params should be optional.

cc @yiyixuxu @sayakpaul @DN6