Use canonical FFE fixtures

[leoromanovsky]

Motivation

Make DataDog/ffe-system-test-data the canonical source for FFE/OpenFeature JSON fixtures in dd-trace-java. This removes copied smoke-test fixtures and moves evaluator behavior coverage to the shared corpus. Depends on DataDog/ffe-system-test-data#9.

Changes

• Add dd-smoke-tests/openfeature/src/test/resources/ffe-system-test-data as a git submodule pinned to the canonical fixture update.
• Remove copied OpenFeature fixture JSON resources.
• Update the smoke test to load canonical ufc-config.json and all sorted evaluation-cases/*.json files.
• Assert canonical result values and reasons from the JSON corpus.
• Remove the stale programmatic evaluator fixture set in favor of the canonical JSON-driven loop.
• Fix the OpenFeature smoke CodeNarc violation by removing an unnecessary Groovy import.
• Add weekly Dependabot gitsubmodule updates.

Decisions

• Shared evaluator behavior must come from JSON fixtures in ffe-system-test-data, not programmatic or copied fixture sets.
• dd-trace-java already supports submodules and recursive checkout in CI; this PR uses the same pattern for the OpenFeature fixture corpus.
• PHP is intentionally excluded until its OpenFeature client lands.

Validation

• JAVA_HOME=/opt/homebrew/opt/openjdk@17/libexec/openjdk.jdk/Contents/Home PATH=/opt/homebrew/opt/openjdk@17/bin:$PATH ./gradlew :dd-smoke-tests:openfeature:codenarcTest
• JAVA_HOME=/opt/homebrew/opt/openjdk@17/libexec/openjdk.jdk/Contents/Home PATH=/opt/homebrew/opt/openjdk@17/bin:$PATH ./gradlew :products:feature-flagging:feature-flagging-api:test --tests datadog.trace.api.openfeature.DDEvaluatorTest