Ensure temporary fix for frontend flaky tests doesn't hide regression on backend tests

Is your feature request related to a problem? Please describe.
Implementation of destination migration, as part of notifications integration, caused some frontend plugin cypress tests to become flaky as the destination used when configuring monitors would be deleted while the tests were running. As a temporary fix while we implement notifications frontend support, we commented out the destination-related logic on the monitor creation/update tests in the following PRs:

1. https://github.com/opensearch-project/alerting-dashboards-plugin/pull/214
2. https://github.com/opensearch-project/opensearch-dashboards-functional-test/pull/182

Describe the solution you'd like
The flaky tests should likely be refactored to configure the monitor using notification channels instead of destinations; but the notifications UX will need to be implemented first to support that.

Describe alternatives you've considered

1. Refactor the flaky tests to only attempt to define actions when the destination list is not empty. This may not be ideal though, as it could reduce thee integrity of tests that are intended to include action definitions.
2. Refactor the flaky tests to not attempt to define actions at all. This may not be ideal though, as the cypress tests are intended to capture the typical end-to-end workflow.

Additional context
Add any other context or screenshots about the feature request here.

Start by reading the monitor creation and update test changes in alerting-dashboards-plugin#214 and opensearch-dashboards-functional-test#182. Review how destination migration affects the Cypress tests and how notification channels and frontend support are expected to replace destinations. Done means the end-to-end action coverage is restored without masking backend test regressions.