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/fork_choice/src/fork_choice.rs

@@ -13,7 +13,7 @@ use std::cmp::Ordering;
 use std::collections::BTreeSet;
 use std::marker::PhantomData;
 use std::time::Duration;
-use tracing::{debug, warn};
+use tracing::{debug, instrument, warn};
 use types::{
     consts::bellatrix::INTERVALS_PER_SLOT, AbstractExecPayload, AttestationShufflingId,
     AttesterSlashingRef, BeaconBlockRef, BeaconState, BeaconStateError, ChainSpec, Checkpoint,
@@ -472,6 +472,7 @@ where
     /// Is equivalent to:
     ///
     /// https://github.com/ethereum/eth2.0-specs/blob/v0.12.1/specs/phase0/fork-choice.md#get_head
+    #[instrument(skip_all, level = "debug")]
     pub fn get_head(
         &mut self,
         system_time_current_slot: Slot,
@@ -646,6 +647,12 @@ where
     /// The supplied block **must** pass the `state_transition` function as it will not be run
     /// here.
     #[allow(clippy::too_many_arguments)]
+    #[instrument(
+        name = "fork_choice_on_block",
+        skip_all,
+        fields(
+            fork_choice_block_delay = ?block_delay
+        ))]
     pub fn on_block<Payload: AbstractExecPayload<E>>(
         &mut self,
         system_time_current_slot: Slot,