Add LastFullSnapshotSlot to SnapshotConfig (#19341)

runtime/src/snapshot_config.rs

@@ -1,7 +1,10 @@
 use crate::snapshot_utils::ArchiveFormat;
 use crate::snapshot_utils::SnapshotVersion;
 use solana_sdk::clock::Slot;
-use std::path::PathBuf;
+use std::{
+    path::PathBuf,
+    sync::{Arc, RwLock},
+};
 
 /// Snapshot configuration and runtime information
 #[derive(Clone, Debug)]
@@ -26,4 +29,9 @@ pub struct SnapshotConfig {
 
     /// Maximum number of full snapshot archives to retain
     pub maximum_snapshots_to_retain: usize,
+
+    /// Runtime information of the last full snapshot slot
+    pub last_full_snapshot_slot: LastFullSnapshotSlot,
 }
+
+pub type LastFullSnapshotSlot = Arc<RwLock<Option<Slot>>>;