fix(blackhole sink): disable rate limiting for periodic stats messages (#24190)

* fix(blackhole sink): disable rate limiting for periodic stats messages

The blackhole sink's informational "Collected events" messages were being
rate-limited since rate limiting was enabled by default in #24024. This is
undesirable because:

1. These are deliberately scheduled periodic messages (controlled by the
   `print_interval_secs` config option), not error conditions that could
   flood the logs
2. Users explicitly configure the frequency - rate limiting defeats that
   explicit configuration and breaks user expectations
3. The interval timer already prevents log flooding, making additional
   rate limiting redundant
4. The blackhole sink is used for debugging/testing, where predictable
   output is essential

This fix adds `internal_log_rate_limit = false` to both info! calls,
similar to how the console sink disables rate limiting for its critical
operational messages.

Fixes #24188

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

* chore: add changelog fragment for blackhole sink rate limiting fix

---------

Co-authored-by: Claude <[email protected]>

Author: 2 people

changelog.d/24188_blackhole_sink_rate_limiting.fix.md

@@ -0,0 +1,3 @@
+The `blackhole` sink's periodic statistics messages (controlled by `print_interval_secs`) are no longer incorrectly suppressed by rate limiting. These informational messages now appear at the user-configured interval as expected.
+
+authors: pront

src/sinks/blackhole/sink.rs

@@ -65,6 +65,7 @@ impl StreamSink<EventArray> for BlackholeSink {
                             info!(
                                 events = total_events.load(Ordering::Relaxed),
                                 raw_bytes_collected = total_raw_bytes.load(Ordering::Relaxed),
+                                internal_log_rate_limit = false,
                                 "Collected events."
                             );
                         },
@@ -75,6 +76,7 @@ impl StreamSink<EventArray> for BlackholeSink {
                 info!(
                     events = total_events.load(Ordering::Relaxed),
                     raw_bytes_collected = total_raw_bytes.load(Ordering::Relaxed),
+                    internal_log_rate_limit = false,
                     "Collected events."
                 );
             });