Internal interface to provide the core writer to the tracer. The com.openobserve.trace.core.CoreTracer uses this interface to be able to provide custom implementations of the writer. By using this interface, the tracer can be decoupled from the oo-sdk-android-trace-otel module by providing the writer implementation from the oo-sdk-android-trace module. The reason we cannot provide the implementation directly in the oo-track-android-trace-otel module is that the current Writer implementation is depending on too many classes from the oo-sdk-android-trace module.