fix: Add runtime DeprecationWarnings to deprecated methods

[jsonbailey]

Summary

• client.py: config(), create_chat(), agent(), and agents() were documented as deprecated in docstrings but emitted no runtime signal (create_chat used log.warning instead). All four now emit warnings.warn(..., DeprecationWarning, stacklevel=2).
• tracker.py: track_openai_metrics() now emits a DeprecationWarning pointing callers to track_metrics_of with get_ai_metrics_from_response from ldai_openai.
• All deprecated docstrings normalized to the consistent RST form: .. deprecated:: Use :meth:X instead. This method will be removed in a future version.

This is consistent with the pattern used in launchdarkly-server-sdk.

Test plan

• test_tracker.py updated — both track_openai_metrics tests assert DeprecationWarning via pytest.warns
• track_bedrock_converse_metrics intentionally left unchanged (bedrock package planned separately)

Closes AIC-1663

🤖 Generated with Claude Code

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Note

Low Risk
Low risk: behavior is unchanged aside from emitting runtime DeprecationWarnings, which may surface in caller test output or warning-as-error environments.

Overview
Adds runtime DeprecationWarnings (with stacklevel=2) to previously docstring-only deprecated APIs in LDAIClient (e.g. config, create_chat, agent, agents) and to LDAIConfigTracker.track_openai_metrics, replacing the prior log-only signal.

Updates test_tracker.py to assert the new warning behavior via pytest.warns while keeping existing tracking semantics.

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