feat: kvbm-logical (#6033)

Signed-off-by: Ryan Olson <rolson@nvidia.com>

lib/kvbm-logical/src/metrics/mod.rs

+// SPDX-FileCopyrightText: Copyright (c) 2024-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+//! Prometheus metrics for block pool observability.
+//!
+//! Architecture:
+//! - [`BlockPoolMetrics`]: Raw `AtomicU64`/`AtomicI64` counters and gauges. Zero overhead on hot path.
+//! - [`MetricsAggregator`]: Custom `prometheus::core::Collector` that reads atomics at scrape time.
+//! - [`StatsCollector`]: Optional periodic sampler computing rates, gradients, and hit ratios.
+
+mod collector;
+mod pool_metrics;
+mod stats;
+
+pub use collector::MetricsAggregator;
+pub use pool_metrics::{BlockPoolMetrics, MetricsSnapshot};
+pub use stats::{StatsCollector, StatsConfig, StatsSnapshot};
+
+/// Returns the short (unqualified) type name for `T`.
+///
+/// Strips generic parameters and the module path, returning only the base
+/// type name. May still be imperfect for deeply nested or anonymous types.
+pub fn short_type_name<T: 'static>() -> String {
+    let full = std::any::type_name::<T>();
+    let base = full.split_once('<').map(|(b, _)| b).unwrap_or(full);
+    base.rsplit("::").next().unwrap_or(base).to_string()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    struct MyType;
+
+    #[test]
+    fn test_short_type_name() {
+        let name = short_type_name::<MyType>();
+        assert_eq!(name, "MyType");
+    }
+
+    #[test]
+    fn test_short_type_name_primitive() {
+        let name = short_type_name::<u32>();
+        assert_eq!(name, "u32");
+    }
+
+    #[test]
+    fn test_short_type_name_generic() {
+        let name = short_type_name::<Vec<String>>();
+        assert_eq!(name, "Vec");
+    }
+}