Instrument tracing spans for block processing and import (#7816)

#7815

- removes all existing spans, so some span fields that appear in logs like `service_name` may be lost.
- instruments a few key code paths in the beacon node, starting from **root spans** named below:

* Gossip block and blobs
* `process_gossip_data_column_sidecar`
* `process_gossip_blob`
* `process_gossip_block`
* Rpc block and blobs
* `process_rpc_block`
* `process_rpc_blobs`
* `process_rpc_custody_columns`
* Rpc blocks (range and backfill)
* `process_chain_segment`
* `PendingComponents` lifecycle
* `pending_components`

To test locally:
* Run Grafana and Tempo with https://github.com/sigp/lighthouse-metrics/pull/57
* Run Lighthouse BN with `--telemetry-collector-url http://localhost:4317`

Some captured traces can be found here: https://hackmd.io/@jimmygchen/r1sLOxPPeg

Removing the old spans seem to have reduced the memory usage quite a lot - i think we were using them on long running tasks and too excessively:
<img width="910" height="495" alt="image" src="https://github.com/user-attachments/assets/5208bbe4-53b2-4ead-bc71-0b782c788669" />

beacon_node/network/src/router.rs

@@ -23,7 +23,7 @@ use std::sync::Arc;
 use std::time::{Duration, SystemTime, UNIX_EPOCH};
 use tokio::sync::mpsc;
 use tokio_stream::wrappers::UnboundedReceiverStream;
-use tracing::{debug, error, info_span, trace, warn, Instrument};
+use tracing::{debug, error, trace, warn};
 use types::{BlobSidecar, DataColumnSidecar, EthSpec, ForkContext, SignedBeaconBlock};
 
 /// Handles messages from the network and routes them to the appropriate service to be handled.
@@ -132,7 +132,6 @@ impl<T: BeaconChainTypes> Router<T> {
                 debug!("Network message router started");
                 UnboundedReceiverStream::new(handler_recv)
                     .for_each(move |msg| future::ready(handler.handle_message(msg)))
-                    .instrument(info_span!("", service = "router"))
                     .await;
             },
             "router",