Missing tracer provider shutdown — spans may be lost on exit.

[scarmuega]

In @src/bin/dolos/common.rs around lines 145 - 168, The SdkTracerProvider
created and set globally is never shutdown, so buffered spans can be lost;
modify the tracing setup to either return the created SdkTracerProvider (the
provider variable returned from SdkTracerProvider::builder()) from
setup_tracing() so callers can call provider.shutdown() (or
provider.force_flush() where available) during cleanup (e.g., alongside
pipeline.teardown() in run_pipeline), or explicitly call
opentelemetry::global::shutdown_tracer_provider() before process exit for code
paths that don't use run_pipeline; ensure you reference the created provider
(SdkTracerProvider) and invoke provider.shutdown() or
opentelemetry::global::shutdown_tracer_provider() at process teardown to flush
the batch exporter.