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/beacon_chain/src/kzg_utils.rs

@@ -5,6 +5,7 @@ use kzg::{
 use rayon::prelude::*;
 use ssz_types::{FixedVector, VariableList};
 use std::sync::Arc;
+use tracing::instrument;
 use types::beacon_block_body::KzgCommitments;
 use types::data_column_sidecar::{Cell, DataColumn, DataColumnSidecarError};
 use types::{
@@ -163,6 +164,7 @@ pub fn verify_kzg_proof<E: EthSpec>(
 }
 
 /// Build data column sidecars from a signed beacon block and its blobs.
+#[instrument(skip_all, level = "debug", fields(blob_count = blobs.len()))]
 pub fn blobs_to_data_column_sidecars<E: EthSpec>(
     blobs: &[&Blob<E>],
     cell_proofs: Vec<KzgProof>,