Add docstrings to state and stats

[Vaibhavdixit02]

Checklist

• [ ] Appropriate tests were added
• [ ] Any code changes were done in a way that does not break public API
• [ ] All documentation related to code changes were updated
• [ ] The new code follows the contributor guidelines, in particular the SciML Style Guide and COLPRAC.
• [ ] Any new documentation only uses public API

Additional context

Add any other context about the problem here.

[codecov[bot]]

Codecov Report

Attention: 8 lines in your changes are missing coverage. Please review.

Comparison is base (31e2dbe) 8.93% compared to head (35b97e5) 8.93%.

Files	Patch %	Lines
lib/OptimizationFlux/src/OptimizationFlux.jl	0.00%	3 Missing :warning:
lib/OptimizationBBO/src/OptimizationBBO.jl	0.00%	1 Missing :warning:
...onStrategy/src/OptimizationCMAEvolutionStrategy.jl	0.00%	1 Missing :warning:
lib/OptimizationMOI/src/nlp.jl	0.00%	1 Missing :warning:
lib/OptimizationOptimJL/src/OptimizationOptimJL.jl	66.66%	1 Missing :warning:
lib/OptimizationOptimisers/src/sophia.jl	0.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #657 +/- ## ====================================== Coverage 8.93% 8.93% ====================================== Files 31 31 Lines 2506 2506 ====================================== Hits 224 224 Misses 2282 2282 ```

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