Show the Start time relative to "Navigation::Start" in the Marker Table

In the Marker Table, currently the "Start" column shows the time from the beginning of the profile.
When comparing two profiles for the browsertime benchmark, I want to see the time from the "Navigation::Start", so that it's easier to compare two profiles (opened in two adjacent tabs) and see the difference in the timing between them.

The similar thing can be done in the Marker Chart, but the Marker Chart doesn't show the Details label for short markers, and it's hard to compare multiple events at once.

┆Issue is synchronized with this [Jira Task](https://mozilla-hub.atlassian.net/browse/FP-957)