Instrument attestation signing. (#8508)

We noticed attestation signing taking 2+ seconds on some of our hoodi nodes and the current traces doesn't provide enough details. This PR adds a few more spans to the `attestation_duty_cycle` code path in the VC.

Before:
<img width="842" height="154" alt="image" src="https://github.com/user-attachments/assets/cfc5c8c0-e6f2-4f56-a8e4-65001af4a005" />

After:
<img width="496" height="217" alt="image" src="https://github.com/user-attachments/assets/c91cfa88-af1b-456e-8c64-625809eb6881" />


  


Co-Authored-By: Jimmy Chen <jchen.tc@gmail.com>

validator_client/slashing_protection/src/slashing_database.rs

@@ -11,6 +11,7 @@ use rusqlite::{OptionalExtension, Transaction, TransactionBehavior, params};
 use std::fs::File;
 use std::path::Path;
 use std::time::Duration;
+use tracing::instrument;
 use types::{AttestationData, BeaconBlockHeader, Epoch, Hash256, PublicKeyBytes, SignedRoot, Slot};
 
 type Pool = r2d2::Pool<SqliteConnectionManager>;
@@ -639,6 +640,7 @@ impl SlashingDatabase {
     /// to prevent concurrent checks and inserts from resulting in slashable data being inserted.
     ///
     /// This is the safe, externally-callable interface for checking attestations.
+    #[instrument(skip_all, level = "debug")]
     pub fn check_and_insert_attestation(
         &self,
         validator_pubkey: &PublicKeyBytes,