Support Date math in Index Names

[adityaj1107]

Is your feature request related to a problem? Please describe.
Currently the date math pattern in index names for the search query in the monitor input parameters is not allowed via the OSD dashboards. This support is available via the API calls (opensearch-project/alerting#74) for the monitor definition. Support in the OSD for date math pattern in the index names will make it easier to define the monitors using the indices with the date math pattern.

Describe the solution you'd like
Support to list and validate the Indices defined via the date math index pattern.

Describe alternatives you've considered
Able to create monitors for indices defined having the date math pattern via the APIs. However the support via the dashboard for the plugin would be a good addition.