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" />

Cargo.toml

@@ -193,6 +193,9 @@ network = { path = "beacon_node/network" }
 node_test_rig = { path = "testing/node_test_rig" }
 num_cpus = "1"
 once_cell = "1.17.1"
+opentelemetry = "0.30.0"
+opentelemetry-otlp = { version = "0.30.0", features = ["grpc-tonic"] }
+opentelemetry_sdk = "0.30.0"
 operation_pool = { path = "beacon_node/operation_pool" }
 parking_lot = "0.12"
 paste = "1"
@@ -253,6 +256,7 @@ tracing = "0.1.40"
 tracing-appender = "0.2"
 tracing-core = "0.1"
 tracing-log = "0.2"
+tracing-opentelemetry = "0.31.0"
 tracing-subscriber = { version = "0.3", features = ["env-filter", "json"] }
 tree_hash = "0.10.0"
 tree_hash_derive = "0.10.0"