[Tune] Fix ResourceChangingScheduler dropping PGF args

[Yard1]

Signed-off-by: Antoni Baum [email protected]

Why are these changes needed?

ResourceChangingScheduler didn't carry over attributes from the base PlacementGroupFactory, causing the resources to be constantly reallocated as they failed the equality check between the old resources and new resources.

Related issue number

Closes #30265

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[amogkam]

ResourceChangingScheduler changes lgtm.

Can we do the GBDTTrainer changes in a separate PR?

I'd like to see if we can simplify the logic and keep a linear conversion path, rather than the current branched conversion path.

Instead of this:

Scaling Config -> PGF--------------------->Combine -> ...
                                          ^
Scaling Config -> Ray Params -> PGF-------|

Ideally we can just have this

Scaling Config -> PGF

Or at least this

Scaling Config -> Ray Params -> PGF

[Yard1]

Converting a ScalingConfig to PGF directly was the first idea, but the issue is that RayParams for LightGBM has some extra logic/defaults and we don't have an API right now to do the same for ScalingConfig.

Refactored and split into #30470