Add parameter sweep mode + auto-save metadata for batch testing

### Feature Idea

Hi and thanks for ComfyUI — brilliant tool, using it daily.
This is a feature request to improve batch testing and result tracking.

✨ 1. Parameter Sweep Mode
Current batch runs always repeat the same settings (cfg, denoise, etc.) with different seeds.

What would be extremely useful:

Add an option to automatically vary a specific parameter across a batch, like:

cfg: 5 → 15 (step 1)

denoise: 0.1 → 1.0 (step 0.1)

ipadapter_weight: custom list of values (ex: 0.2, 0.4, 0.6, 0.8)

That would let us run controlled experiments without duplicating workflows or manually tweaking nodes for each run.

🗂 2. Auto-naming based on parameters
Allow filename templates like:
{basename}_cfg{cfg}_denoise{denoise}.png
→ so each image clearly shows what config was used.
Currently, names are generic and lose all meaning after a few tests.

🧠 3. Auto-metadata injection
Even with SaveImage, the metadata field is empty unless we manually fill it — which is absurd, since all parameters are already available in the queue system.

Proposal:

Add a simple checkbox: “Auto-fill metadata from current generation”

Or an {auto} keyword that pulls values like cfg, seed, model, workflow_hash, etc.

✅ Why this matters
This would:

Make testing and comparing generations vastly easier

Eliminate manual renaming and metadata editing

Bring ComfyUI closer to a full-featured experimental environment

Thanks for considering!

### Existing Solutions

_No response_

### Other

_No response_