[rocksdb] add metric for num level 0 files (#19230)

## Description 

Too many level 0 files can be a trigger to write stall & stop as well

## Test plan 

CI

---

## Release notes

Check each box that your changes affect. If none of the boxes relate to
your changes, release notes aren't required.

For each box you select, include information after the relevant heading
that describes the impact of your changes that a user might notice and
any actions they must take to implement updates.

- [ ] Protocol: 
- [ ] Nodes (Validators and Full nodes): 
- [ ] Indexer: 
- [ ] JSON-RPC: 
- [ ] GraphQL: 
- [ ] CLI: 
- [ ] Rust SDK:
- [ ] REST API:

crates/typed-store/src/metrics.rs

@@ -78,6 +78,7 @@ pub struct ColumnFamilyMetrics {
     pub rocksdb_total_sst_files_size: IntGaugeVec,
     pub rocksdb_total_blob_files_size: IntGaugeVec,
     pub rocksdb_total_num_files: IntGaugeVec,
+    pub rocksdb_num_level0_files: IntGaugeVec,
     pub rocksdb_current_size_active_mem_tables: IntGaugeVec,
     pub rocksdb_size_all_mem_tables: IntGaugeVec,
     pub rocksdb_num_snapshots: IntGaugeVec,
@@ -124,6 +125,13 @@ impl ColumnFamilyMetrics {
                 registry,
             )
             .unwrap(),
+            rocksdb_num_level0_files: register_int_gauge_vec_with_registry!(
+                "rocksdb_num_level0_files",
+                "Number of level 0 files in the column family",
+                &["cf_name"],
+                registry,
+            )
+            .unwrap(),
             rocksdb_current_size_active_mem_tables: register_int_gauge_vec_with_registry!(
                 "rocksdb_current_size_active_mem_tables",
                 "The current approximate size of active memtable (bytes).",

crates/typed-store/src/rocks/mod.rs

@@ -1006,6 +1006,14 @@ impl<K, V> DBMap<K, V> {
             .rocksdb_total_num_files
             .with_label_values(&[cf_name])
             .set(total_num_files);
+        db_metrics
+            .cf_metrics
+            .rocksdb_num_level0_files
+            .with_label_values(&[cf_name])
+            .set(
+                Self::get_int_property(rocksdb, &cf, &num_files_at_level(0))
+                    .unwrap_or(METRICS_ERROR),
+            );
         db_metrics
             .cf_metrics
             .rocksdb_current_size_active_mem_tables

deny.toml

@@ -34,6 +34,8 @@ ignore = [
     "RUSTSEC-2024-0336",
     # allow yaml-rust being unmaintained
     "RUSTSEC-2024-0320",
+    # allow unmaintained proc-macro-error used in transitive dependencies
+    "RUSTSEC-2024-0370",
 ]
 # Threshold for security vulnerabilities, any vulnerability with a CVSS score
 # lower than the range specified will be ignored. Note that ignored advisories