[ML] Single metric viewer should indicate existence of annotations that are beyond the selected time region

[sophiec20]

The single metric viewer displays annotations that are within the scope of the selected region. However if an annotation exists outside of the selected region, it is invisible. An end-user only gets to see the annotation if they happen to either select the appropriate time range or know where it was beforehand.

It makes sense for the anomaly table and the annotation table to both be limited in scope to the time range selected rather than the kibana time picker. However could there perhaps be an indicator in the time series brush area to show and that annotations exist?

Note that anomaly explorer displays all annotations within the range of the kibana time picker.

Relates to #25856

[elasticmachine]

Pinging @elastic/ml-ui (:ml)