Editing a Per Bucket Monitor loses the Group By expressions

[krsouthern]

What is the bug?

When you edit a Per Bucket Monitor the Group by expressions are not re-populated.

when you click edit on the monitor, the saved values are not displayed

How can one reproduce the bug?
Steps to reproduce the behavior:

1. Create a new Per Bucket Monitor
2. Add some group by expressions in the Query box
3. Save the Monitor
4. Edit the Monitor
5. The Group by expressions are lost

What is the expected behavior?
The Group by expressions should displayed on the screen

What is your host/environment?

• Browser: Safari and Chrome on Mac

Do you have any screenshots?
added screenshots above

Do you have any additional context?
Add any other context about the problem.

[eirsep]

This is an alerting dashboards issue. Created the same issue there: opensearch-project/alerting-dashboards-plugin#858