chore: e2e Android sample - move keys and url into config

[abelonogov-ld]

Summary

• Move keys into config to reduce change of accidental key merge
• add flagEvaluation method on the app launch for further investigations

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Note

Low Risk
Build-time config wiring plus additional debug logging/listeners in an e2e sample; main risk is misconfiguration (empty local.properties values) causing the app to run without a valid SDK key or expected endpoints.

Overview
The Android e2e sample now reads LaunchDarkly configuration from local.properties and exposes it via BuildConfig (LAUNCHDARKLY_MOBILE_KEY, OTLP_ENDPOINT, BACKEND_URL), replacing the previously hardcoded mobile key and wiring the endpoints into ObservabilityOptions.

On app init, BaseApplication now performs a boolVariation for feature1 and registers a FeatureFlagChangeListener to log subsequent changes, aiding investigations and validating flag updates.

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