Feature/upgrade optuna 4.2.1

[dahlem]

Upgrade hydra_optuna_sweeper to Optuna 4.2.1

Summary

This PR upgrades the hydra_optuna_sweeper plugin to use Optuna 4.2.1 (from 3.0.0) and updates the code to comply with the latest
Optuna APIs, replacing deprecated distribution classes and methods.

Changes

• Replace deprecated distribution classes with modern equivalents:
  • DiscreteUniformDistribution → FloatDistribution with step parameter
  • IntUniformDistribution, IntLogUniformDistribution → IntDistribution
  • UniformDistribution, LogUniformDistribution → FloatDistribution
• Update Trial API usage to public methods instead of internal ones
• Update sampler configurations to remove deprecated parameters
• Update tests to reflect the new distribution classes
• Add news entry (enable python3.10 CI for Windows #2444)

Test Plan

• Unit tests for distribution classes and API pass
• Example applications run successfully
• Manual testing with different samplers and storage options

Backward Compatibility

This change maintains backward compatibility with existing configurations.

[charleswilmot]

I need this!

[filyp]

Awesome! I see merging this could resolve a bunch of other issues:
#2562
#2995
#2162
#2360
and maybe more.

The old sweeper is currently unusable for me, so for now I'm installing directly from this PR with:

hydra-optuna-sweeper @ git+https://github.com/dahlem/hydra.git@feature/upgrade-optuna-4.2.1#subdirectory=plugins/hydra_optuna_sweeper

and for me it's working without issues (I'm using TPESampler and various FloatDistributions, both log and uniform).

[amadeuszsz]

@rsokl
Sorry for direct ping recently active maintainer 🙏🏻

Is there any chance to merge this PR?

[omry]

Hi, any breaking changes in the config? (existing configs will continue to work)?

[omry]

Thanks for working on this, and thanks to everyone who tested it.

We are going to consolidate the Optuna v4 work in #3211 instead of keeping two competing upgrade PRs open. #3211 covers the same plugin upgrade path and is the active PR currently being reviewed, so I am closing this one as superseded.

Please follow #3211 for the remaining Optuna v4 work.