Cleanup and reinforce the interface

[BatyLeo]

• circle back to rename maximizer_kwargs to context, as it also holds context and may be used by the maximizer
• clarify_generate_sample interface
• make objective_value more explicit
• clarify generate_environment output type
• make sure DataSample field cannot overlap with kwargs and extra
• minor changes and cleanup

[codecov]

Codecov Report

❌ Patch coverage is 83.58209% with 11 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/Utils/interface.jl	64.70%	6 Missing ⚠️
...icVehicleScheduling/StochasticVehicleScheduling.jl	62.50%	3 Missing ⚠️
...tualStochasticArgmax/ContextualStochasticArgmax.jl	80.00%	2 Missing ⚠️

Files with missing lines	Coverage Δ
ext/DFLBenchmarksPlotsExt.jl	100.00% <ø> (ø)
src/Argmax/Argmax.jl	100.00% <100.00%> (ø)
src/Argmax2D/Argmax2D.jl	100.00% <100.00%> (ø)
src/ContextualStochasticArgmax/policies.jl	100.00% <ø> (ø)
src/DecisionFocusedLearningBenchmarks.jl	100.00% <ø> (ø)
src/FixedSizeShortestPath/FixedSizeShortestPath.jl	94.00% <100.00%> (ø)
src/PortfolioOptimization/PortfolioOptimization.jl	92.30% <100.00%> (+0.41%)	⬆️
src/Ranking/Ranking.jl	100.00% <100.00%> (ø)
src/StochasticVehicleScheduling/policies.jl	81.25% <ø> (ø)
src/SubsetSelection/SubsetSelection.jl	100.00% <100.00%> (ø)
... and 6 more

... and 1 file with indirect coverage changes

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