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" />

consensus/state_processing/src/epoch_cache.rs

@@ -3,6 +3,7 @@ use crate::common::base::SqrtTotalActiveBalance;
 use crate::common::{altair, base};
 use crate::metrics;
 use safe_arith::SafeArith;
+use tracing::instrument;
 use types::epoch_cache::{EpochCache, EpochCacheError, EpochCacheKey};
 use types::{
     ActivationQueue, BeaconState, ChainSpec, EthSpec, FixedBytesExtended, ForkName, Hash256,
@@ -130,6 +131,7 @@ pub fn is_epoch_cache_initialized<E: EthSpec>(
         .is_ok())
 }
 
+#[instrument(skip_all, level = "debug")]
 pub fn initialize_epoch_cache<E: EthSpec>(
     state: &mut BeaconState<E>,
     spec: &ChainSpec,