Add Trackio Callback for Optuna Registry

[ParagEkbote]

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Motivation

As described in the PR, we port the trackio callback from optuna-integration to optuna-registry. A couple of new features have been introduced:

• Automatic syncing of optuna trials with trackio-sync

• Better resume semantics for trials.

Could you please review the changes?

cc: @c-bata

Description of the changes

Included a init.py and callback.py which are the core files of the packages, also included the relevant license and readme file to describe the working of the callback.

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[c-bata]

@gen740 Could you review this PR?

[gen740]

I tried running the example locally, and got:

RuntimeError: Call trackio.init() before trackio.log().

It works fine after adding trackio.init(), but maybe it would be more user-friendly to include that setup in the example?

[ParagEkbote]

There was an issue in the implementation of the callback where __call__() did not correctly initialize the trials for trackio. I have updated the callback implementation to fix this and re-tested with the examples which now work correctly.