[ML] Single Metric Viewer in dashboards: ensure the detector index is set correctly for 'Open' action (#180086)

## Summary

Follow up to https://github.com/elastic/kibana/pull/179364

This PR ensures the detector index is set correctly the url in the `Open
in single metric viewer` action to link from dashboards to ML > Single
metric viewer.

### Checklist

Delete any items that are not applicable to this PR.

- [ ] Any text added follows [EUI's writing
guidelines](https://elastic.github.io/eui/#/guidelines/writing), uses
sentence case text and includes [i18n
support](https://github.com/elastic/kibana/blob/main/packages/kbn-i18n/README.md)
- [ ]
[Documentation](https://www.elastic.co/guide/en/kibana/master/development-documentation.html)
was added for features that require explanation or tutorials
- [ ] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios
- [ ] [Flaky Test
Runner](https://ci-stats.kibana.dev/trigger_flaky_test_runner/1) was
used on any tests changed
- [ ] Any UI touched in this PR is usable by keyboard only (learn more
about [keyboard accessibility](https://webaim.org/techniques/keyboard/))
- [ ] Any UI touched in this PR does not create any new axe failures
(run axe in browser:
[FF](https://addons.mozilla.org/en-US/firefox/addon/axe-devtools/),
[Chrome](https://chrome.google.com/webstore/detail/axe-web-accessibility-tes/lhdoppojpmngadmnindnejefpokejbdd?hl=en-US))
- [ ] If a plugin configuration key changed, check if it needs to be
allowlisted in the cloud and added to the [docker
list](https://github.com/elastic/kibana/blob/main/src/dev/build/tasks/os_packages/docker_generator/resources/base/bin/kibana-docker)
- [ ] This renders correctly on smaller devices using a responsive
layout. (You can test this [in your
browser](https://www.browserstack.com/guide/responsive-testing-on-local-server))
- [ ] This was checked for [cross-browser
compatibility](https://www.elastic.co/support/matrix#matrix_browsers)

x-pack/plugins/ml/public/ui_actions/open_in_single_metric_viewer_action.tsx

@@ -59,7 +59,7 @@ export function createOpenInSingleMetricViewerAction(
 
       if (isSingleMetricViewerEmbeddableContext(context)) {
         const { embeddable } = context;
-        const { jobIds, query$, selectedEntities } = embeddable;
+        const { jobIds, query$, selectedEntities, selectedDetectorIndex } = embeddable;
 
         return locator.getUrl(
           {
@@ -75,6 +75,7 @@ export function createOpenInSingleMetricViewerAction(
               jobIds: jobIds.getValue(),
               query: query$?.getValue(),
               entities: selectedEntities?.getValue(),
+              detectorIndex: selectedDetectorIndex?.getValue(),
             },
           },
           { absolute: true }