"Set selection start time here" in the marker table context menu should scroll to the top

In the marker table, when using the "Set selection start time here" context menu item, currently the selected index remains the same, but due to changing the selection, all the markers before the selected one disappear. We should move the selection to the first marker in the new list, so that the selected marker remains the same.

┆Issue is synchronized with this [Jira Task](https://mozilla-hub.atlassian.net/browse/FP-134)