Add quieter debug logging API for beam developers.

This would be useful to catch mistakes which should not necessarily fail a pipeline (i.e. a metric missing required metdata should be dropped and quietly logged). Logging this every time the metric is produced would be noisy,

an API like log every n occurances or log once ever n seconds would help surface these without filling the logs with spam.

See TODO markers for this Jira issue as well to find some places to add this.

Imported from Jira [BEAM-7191](https://issues.apache.org/jira/browse/BEAM-7191). Original Jira may contain additional context.
Reported by: ajamato@google.com.