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" />

slasher/service/src/service.rs

@@ -20,7 +20,7 @@ use std::sync::Arc;
 use task_executor::TaskExecutor;
 use tokio::sync::mpsc::UnboundedSender;
 use tokio::time::{interval_at, Duration, Instant};
-use tracing::{debug, error, info, info_span, trace, warn, Instrument};
+use tracing::{debug, error, info, trace, warn};
 use types::{AttesterSlashing, Epoch, EthSpec, ProposerSlashing};
 
 pub struct SlasherService<T: BeaconChainTypes> {
@@ -64,15 +64,12 @@ impl<T: BeaconChainTypes> SlasherService<T> {
                 update_period,
                 slot_offset,
                 notif_sender,
-            )
-            .instrument(tracing::info_span!("slasher", service = "slasher")),
+            ),
             "slasher_server_notifier",
         );
 
         executor.spawn_blocking(
             || {
-                let span = info_span!("slasher", service = "slasher");
-                let _ = span.enter();
                 Self::run_processor(beacon_chain, slasher, notif_receiver, network_sender);
             },
             "slasher_server_processor",