feat(v7)!: Remove deprecated APIs, Pydantic models

[khvn26]

In this PR, we remove deprecated interfaces:

• get_identity_feature_state
• get_identity_feature_states
• get_identity_segments
• get_context_segments
• get_environment_feature_state
• get_environment_feature_states
  and all the Pydantic models representing the Core API entities.

Only get_evaluation_result, along with EvaluationContext and EvaluationResult types, are now exported by the engine.

The following functionality isn't managed by the engine anymore:

• Sorting the multivariate feature states by id – variants are expected to be pre-sorted.
• Filtering resulting flags based on project/environment hide_disabled_flags attributes.
• Mapping Core API entities to engine typed dicts, and vice versa — there is, however, adapting code to map engine-test-data to evaluation contexts.

[github-actions]

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Generated by 🐒 cobertura-action against 988984f

[codspeed-hq]

CodSpeed Performance Report

Merging #250 will not alter performance

_{Comparing feat/drop-pydantic-models (988984f) with main (f99fa99)}

Summary

✅ 1 untouched benchmarks

[gagantrivedi]

Looks good apart from one minor question/comment

[emyller]

Looks good with minor optional comments.

[emyller]

Looks great

Gagan is OOO and the only outstanding thread was resolved.