fix: update ProviderEvaluationBuilder usage for OpenFeature SDK 1.21.0 compatibility

[kinyoklion]

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

OpenFeature Java SDK 1.21.0 changed ProviderEvaluationBuilder from having 1 type parameter to 3 (adopting Lombok's @SuperBuilder pattern). This causes a compilation failure since the provider declares the builder with an explicit single-parameter type.

Describe the solution you've provided

- ProviderEvaluation.ProviderEvaluationBuilder<T> builder = ProviderEvaluation.<T>builder()
+ var builder = ProviderEvaluation.<T>builder()

Using var lets the compiler infer the correct builder type regardless of the OpenFeature SDK version. The var keyword is already used elsewhere in the codebase (e.g., Provider.java). All 43 existing tests pass with this change against OpenFeature SDK 1.21.0.

Describe alternatives you've considered

• Explicitly using ProviderEvaluation.ProviderEvaluationBuilder<T, ?, ?> — works but couples the code to the new 3-param signature and wouldn't compile against older SDK versions.

Additional context

Versions tested: OpenFeature SDK 1.21.0, LaunchDarkly Java Server SDK 7.14.0. The version constraint [1.16.0,2.0.0) was already compatible — only the source code needed updating.

Link to Devin session: https://app.devin.ai/sessions/4c170c73c83d42e59b487f8b6fd21cc2
Requested by: @kinyoklion

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Note

Low Risk
Single-line typing change in evaluation detail conversion; no runtime logic changes.

Overview
Fixes a compile break with OpenFeature Java SDK 1.21.0, where ProviderEvaluationBuilder gained extra type parameters.

In EvaluationDetailConverter.getProviderEvaluation, the local builder is now declared with var instead of ProviderEvaluation.ProviderEvaluationBuilder<T>, so the compiler picks the right builder type across SDK versions. Evaluation mapping behavior is unchanged (value, reason, error code, variant).

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[kinyoklion]

Introduced by open-feature/java-sdk#1901