feat: Support OpenFeature tracking

[kinyoklion]

Implements the OpenFeature tracking API in the Ruby provider so experimentation metric events reach LaunchDarkly.

• Adds Provider#track, mapping TrackingEventDetails#fields to the LD custom event data and #value to metric_value.
• A track call without an evaluation context logs a warning and sends nothing, since LaunchDarkly requires a context to associate the event with.
• Raises the openfeature-sdk floor to >= 0.6.1 (< 0.7.0); TrackingEventDetails and Client#track do not exist in 0.6.0.

Implementation details

Requirements

• I have added test coverage for new or changed functionality
• I have followed the repository's pull request submission guidelines
• I have validated my changes against all supported platform versions

Related issues

Part of an audit of the LaunchDarkly OpenFeature providers against the current OpenFeature specification. Tracking (spec section 6) was unimplemented here, and per spec 6.1.4 the OpenFeature SDK silently no-ops when a provider lacks track, so events were being dropped without any error.

Describe the solution you've provided

OpenFeature::SDK::Client#track forwards to provider.track(name, evaluation_context:, tracking_event_details:). The provider converts the evaluation context with the existing EvaluationContextConverter and calls LDClient#track(event_name, context, data, metric_value). Empty fields are normalized to nil so no empty hash is attached to the event.

Describe alternatives you've considered

Sending the event with an anonymous/placeholder context when no evaluation context is supplied — rejected, because it would attribute metric events to a context the application never used. Warning and dropping matches the behavior of the Python provider.

Testing

bundle exec rake (RSpec + RuboCop) on Ruby 3.4: 57 examples, 0 failures; 12 files inspected, no offenses. Ruby 3.4 was used because the gemspec requires >= 3.4.

@cursor review

Link to Devin session: https://app.devin.ai/sessions/0c452d209ec54b068ba120b4c92b8f6c
Requested by: @kinyoklion

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Note

Overview
Implements the OpenFeature tracking API on LaunchDarkly::OpenFeature::Provider so experimentation metric events are forwarded to LaunchDarkly instead of being silently dropped when the provider lacked track.

Provider#track converts the evaluation context via the existing converter and calls LDClient#track, mapping TrackingEventDetails#fields to custom event data and #value to the metric value; empty fields are passed as nil. Calls without an evaluation context log a warning and do not send an event.

The gemspec bumps the openfeature-sdk floor to >= 0.6.1 (< 0.7.0) because TrackingEventDetails and client tracking support are not in 0.6.0. Specs cover basic tracking, event details, and the no-context path.

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