Use new histogram macro to report QP warmup time

Notes:
- The name of the metric used a `.` instead of `_` in `query_planning`.
  Is it breaking to change that? I'm not sure I understand the
  difference

apollo-router/src/plugins/telemetry/utils.rs

@@ -20,7 +20,11 @@ impl TracingUtils for bool {
 /// Timer implementing Drop to automatically compute the duration between the moment it has been created until it's dropped
 ///```ignore
 /// Timer::new(|duration| {
-///     tracing::info!(histogram.apollo_router_test = duration.as_secs_f64());
+///     f64_histogram!(
+///         "apollo_router_test",
+///         "Time spent testing the timer",
+///         duration.as_secs_f64()
+///     );
 /// })
 /// ```
 pub(crate) struct Timer<F>

apollo-router/src/query_planner/caching_query_planner.rs

@@ -173,8 +173,10 @@ where
         experimental_pql_prewarm: &PersistedQueriesPrewarmQueryPlanCache,
     ) {
         let _timer = Timer::new(|duration| {
-            ::tracing::info!(
-                histogram.apollo.router.query.planning.warmup.duration = duration.as_secs_f64()
+            f64_histogram!(
+                "apollo.router.query_planning.warmup.duration",
+                "Time spent warming up the query planner queries in seconds",
+                duration.as_secs_f64()
             );
         });