Monitoring: trace history, trace search, and x:Trace over the stored traces (MON-10 to MON-17, MON-32)

A lossy collector subscriber keeps each inbound SMTP session that reached
MAIL FROM and each delivery attempt, info level and above and never raw
I/O, at most 1,000 events with strings cut at 4 KiB, and writes it when
the span closes as an x:Trace under the telemetry key class, scheduling
its indexing. The index task builds a document of event types, queue ids
and keywords when indexTelemetry is on. x:Trace/get derives timestamp,
from, to and size; /query filters by opening event, text, queueId and
time; /set destroys only. The data purge honours holdTracesFor. The shared
tracing and webhook suites run.

tests/src/telemetry/mod.rs

@@ -7,9 +7,7 @@
 #[cfg(feature = "pending-rebuild")] // inbuxa: pending-rebuild, see docs/spec/features/
 pub mod alerts;
 pub mod metrics;
-#[cfg(feature = "pending-rebuild")] // inbuxa: pending-rebuild, see docs/spec/features/
 pub mod tracing;
-#[cfg(feature = "pending-rebuild")] // inbuxa: pending-rebuild, see docs/spec/features/
 pub mod webhooks;
 
 use crate::utils::server::TestServerBuilder;
@@ -61,9 +59,7 @@ pub async fn telemetry_tests() {
     #[cfg(feature = "pending-rebuild")]
     alerts::test(&test).await;
     metrics::test(&test).await;
-    #[cfg(feature = "pending-rebuild")]
     tracing::test(&test).await;
-    #[cfg(feature = "pending-rebuild")]
     webhooks::test(&test).await;
 
     if test.is_reset() {