This commit enhances the `ScheduledAnnotationBeanPostProcessor` to
instrument `@Scheduled` methods declared on beans. This will create
`"tasks.scheduled.execution"` observations for each execution of a
scheduled method. This supports both blocking and reactive variants.
By default, observations are no-ops; developers must configure the
current `ObservationRegistry` on the `ScheduledTaskRegistrar` by using a
`SchedulingConfigurer`.
Closes gh-29883
09cb844421