Refactor: rename handler package/classes and services from V2Ray*/V2ray* to Core*/Core (e.g. V2rayConfigManager -> CoreConfigManager, V2RayNativeManager -> CoreNativeManager, V2RayServiceManager -> CoreServiceManager, and service classes V2RayVpnService/V2RayProxyOnlyService/V2RayTestService -> CoreVpnService/CoreProxyOnlyService/CoreTestService). Update AndroidManifest service entries and all imports/usages across the app (notifications, receivers, widgets, UI, services, workers) to reference the renamed classes and package (com.v2ray.ang.core). Comments and references were adjusted to match the new names; no functional logic changes intended.