Draw markers that have the same name with the same color

This is related to #1676 but is not quite the same.

For markers that only exist in the marker view, and don't otherwise have a color (they are always drawn blue), it would be nice if they would be drawn with a color based on their name, so that markers of the same name have the same color, to visually understand what is going on.

┆Issue is synchronized with this [Jira Task](https://mozilla-hub.atlassian.net/browse/FP-417)